# 10.3 Phase transitions  (Page 7/21)

 Page 7 / 21

## Total heat needed to change temperature and phase for a substance

How much heat is required to convert 135 g of ice at −15 °C into water vapor at 120 °C?

## Solution

The transition described involves the following steps:

1. Heat ice from −15 °C to 0 °C
2. Melt ice
3. Heat water from 0 °C to 100 °C
4. Boil water
5. Heat steam from 100 °C to 120 °C

The heat needed to change the temperature of a given substance (with no change in phase) is: q = m $×$ c $×$ Δ T (see previous chapter on thermochemistry). The heat needed to induce a given change in phase is given by q = n $×$ Δ H .

Using these equations with the appropriate values for specific heat of ice, water, and steam, and enthalpies of fusion and vaporization, we have:

${q}_{\text{total}}={\left(m\text{⋅}c\text{⋅}\text{Δ}T\right)}_{\text{ice}}+n\text{⋅}\text{Δ}{H}_{\text{fus}}+{\left(m\text{⋅}c\text{⋅}\text{Δ}T\right)}_{\text{water}}+n\text{⋅}\text{Δ}{H}_{\text{vap}}+{\left(m\text{⋅}c\text{⋅}\text{Δ}T\right)}_{\text{steam}}$
$\begin{array}{}\\ \\ =\left(\text{135 g}\text{⋅}\text{2.09 J/g}\text{⋅}\text{°}\text{C}\text{⋅}15\text{°}\text{C}\right)+\left(135\text{⋅}\frac{\text{1 mol}}{18.02\phantom{\rule{0.2em}{0ex}}\text{g}}\text{⋅}\text{6.01 kJ/mol}\right)\phantom{\rule{0.2em}{0ex}}\\ +\left(\text{135 g}\text{⋅}\text{4.18 J/g}\text{⋅}\text{°}\text{C}\text{⋅}100\text{°}\text{C}\right)+\left(\text{135 g}\text{⋅}\frac{\text{1 mol}}{18.02\phantom{\rule{0.2em}{0ex}}\text{g}}\text{⋅}\text{40.67 kJ/mol}\right)\\ +\left(\text{135 g}\text{⋅}\text{1.84 J/g}\text{⋅}\text{°}\text{C}\text{⋅}20\text{°}\text{C}\right)\\ =\text{4230 J}+\text{45.0 kJ}+\text{56,500 J}+\text{305 kJ}+\text{4970 J}\end{array}$

Converting the quantities in J to kJ permits them to be summed, yielding the total heat required:

$=4.23\phantom{\rule{0.2em}{0ex}}\text{kJ}+\text{45.0 kJ}+\text{56.5 kJ}+\text{305 kJ}+\text{4.97 kJ}=\text{416 kJ}$

What is the total amount of heat released when 94.0 g water at 80.0 °C cools to form ice at −30.0 °C?

40.5 kJ

## Key concepts and summary

Phase transitions are processes that convert matter from one physical state into another. There are six phase transitions between the three phases of matter. Melting, vaporization, and sublimation are all endothermic processes, requiring an input of heat to overcome intermolecular attractions. The reciprocal transitions of freezing, condensation, and deposition are all exothermic processes, involving heat as intermolecular attractive forces are established or strengthened. The temperatures at which phase transitions occur are determined by the relative strengths of intermolecular attractions and are, therefore, dependent on the chemical identity of the substance.

## Key equations

• $P=A{e}^{-\text{Δ}{H}_{\text{vap}}\text{/}RT}$
• $\text{ln}\phantom{\rule{0.2em}{0ex}}P=-\frac{\text{Δ}{H}_{\text{vap}}}{RT}\phantom{\rule{0.2em}{0ex}}+\text{ln}\phantom{\rule{0.2em}{0ex}}A$
• $\text{ln}\phantom{\rule{0.2em}{0ex}}\left(\frac{{P}_{2}}{{P}_{1}}\right)\phantom{\rule{0.2em}{0ex}}=\phantom{\rule{0.2em}{0ex}}\frac{\text{Δ}{H}_{\text{vap}}}{R}\phantom{\rule{0.2em}{0ex}}\left(\frac{1}{{T}_{1}}\phantom{\rule{0.2em}{0ex}}-\phantom{\rule{0.2em}{0ex}}\frac{1}{{T}_{2}}\right)$

## Chemistry end of chapter exercises

Heat is added to boiling water. Explain why the temperature of the boiling water does not change. What does change?

Heat is added to ice at 0 °C. Explain why the temperature of the ice does not change. What does change?

The heat is absorbed by the ice, providing the energy required to partially overcome intermolecular attractive forces in the solid and causing a phase transition to liquid water. The solution remains at 0 °C until all the ice is melted. Only the amount of water existing as ice changes until the ice disappears. Then the temperature of the water can rise.

What feature characterizes the dynamic equilibrium between a liquid and its vapor in a closed container?

Identify two common observations indicating some liquids have sufficient vapor pressures to noticeably evaporate?

We can see the amount of liquid in an open container decrease and we can smell the vapor of some liquids.

Does Ethers has hydrogen bonding with water?
ethers lack the hydroxyl groups of alcohols. when ether is placed in water both hydrogen atoms are replaced by alkyl or aryl groups. because ether lacks the O-H bond ether molecules cannot engage in hydrogen bonding with each other.
Jallal
however ethers do have nonbonding electron pairs on their oxygen atoms which allows them to form hydrogen bonds with other molecules such as alcohol raise or a amines that have O-H or N-H bonds.
Jallal
such as alcohols or amines* I always have. typo problem. I need to proofread before I send
Jallal
please what is the a difference between a compound and molecular formula
A compound is just a combination of different element showing their molecular formulation like h2o... A molecular formula is a formular showing the number if moles of each element in a compound
Its
a compound is made up of different atoms help together by ionic bonds in a fixed ratio. example formula is: NaCl or salt. a moleculer compound is consists of two or more atoms held together by covalent bonds. example formula is: H2, O2. the atoms can be the same or different such as CO2 or PCl5
Jallal
Yes, exactly what Its said is correct
Jallal
explain why the number of electron in the shells of elements making up the period of the periodic table following the pattern 2,8,18,32,50
these shells of elections emanating from the core on outward can hold only a certain amount of elections. the Pauli Exclusion rule states that no two elections can occupy the same space. an atom will always to fill all it's shells to maximum with the outer most shell called the valence shell.
Jallal
the first shell closet to the nucleus can hold only two elections. the second shell can hold 8 elections. the third shell can hold 18 elections. the fourth shell can hold 32 elections. the fifth shell can hold 50 elections. point people the atom will try to fully complete it's outer shells
Jallal
this cannot always be done though. the final outermost orbital she'll is called the valence shell and that is what determines it's reactivity. Hence the reason they're placed on the periodic table in that order
Jallal
Noble elements on the furthest right hand side of the periodic table of elements are also called inert because they don't react to other elements because they have all that shells already filled
Jallal
the valence shell also determines the chemicals properties of the atom.
Jallal
The general formula is that the (n)th shell can in principle hold up to 2(n^2) elections.
Jallal
The ISBN is going through
the ISBN is either a 9 digit number or 13 digit number. all textbooks have both those numbers. it's not a big deal anyway
Jallal
the ISBN didn't work. try looking for the 13 digit number instead
Jallal
thanks jallal
Faith
but pls am having problem with solubility curve
Faith
could you please detail what you're having trouble on exactly regarding solubility?
Jallal
how to find oxidation number of an element
Faith
for instance if you are given a graph to plot and answer the question below is kind of confusing
Faith
if there supposed to be a graph?
Jallal
write out the question to the problem
Jallal
yes
Faith
it's not showing.
Jallal
just write out the exact question
Jallal
u know wat just explain oxidation number seems like solubility curve is meant to be self explanatory
Faith
ok first the basic rules for oxidation
Jallal
1.) atoms in their elemental state have an oxidation number of zero. 2.) atoms in monatomic (single atom) ions have an oxidation number equal to their charge
Jallal
3.) in compounds: fluorine is assigned a -1 oxidation number, oxygen is usually assigned a -2 oxidation number (except in peroxide compounds where it is -1, and in binary compounds with fluorine where it is positive); and hydrogen is usually assigned a +1 oxidation number except when it exists
Jallal
okay
Faith
as the hydride ion, H^-,
Jallal
4.) in compounds, all other atoms are assigned an oxidation number so that the sum of the oxidation numbers on all the atoms in the species equals a charge on the species
Jallal
now let's try to determine oxidation state of H2 and H2O
Jallal
using rule 1 H2 is already in its elemental state so it's oxidation number is 0
Jallal
for H2O we we must get the sum of all the oxidation numbers using formula (oxidation # of O x # of O atoms) + (oxidation # of H x # of H atoms)
Jallal
already known oxidation number of oxygen and hydrogen the formula will be (-2x1)+(+1x2)=0
Jallal
0 is exactly what we would expect for a neutral molecule and water is neutral.
Jallal
would you like another example?
Jallal
in dis kind of question that says that what is the oxidation number of z in k3 zcl6 how am I to do it
Faith
k has an oxidation number of +1 and Cl is -1. this is because K has one unpaired electron and its outermost shell and is electropositive being a metal while Cl has one unpaired electron in its outermost shell and is electronegative being nonmetal.
Jallal
so to solve it: k3zcl6.3 times 1 + z + -1 times 6=0. 3-6 +z=0. -3+z=0 so z=3
Jallal
every element in the periodic table has an oxidation number unless it's ionized
Jallal
that is how you find those values and work from there
Jallal
thanks alot
Faith
excuse me I meant to write z=+3
Jallal
the oxidation number has to be positive or negative so you must indicate that
Jallal
I hope I was clear enough. also I want to help you with the solubility problem. if you can tell me the question of the problem I can find a solution and help explain it
Jallal
remember to always use the equation I wrote out before to get the sum of oxidation numbers when dealing with compounds
Jallal
What is collision theory
why would you not make potassium chloride from potassium and hydro caloric acids
If HCl and K were to react to form KCl, then they would have to liberate hydrogen gas, but because HCl is an acid it liberates hydrogen gas only if it reacts with very electropositive metals
Rahim
what is the hardest substance
with what scale one would be 💎
coland
diamond a 10
coland
1-10
coland
there is actually other elements that can cut diamonds and also withstand greater hear and temperature than diamonds.
Jallal
What ate the elements?, Jallal
Rahim
Sorry "ate" should be "are".Typing error.
Rahim
Pls Jallal ,can you name those elements because it is only diamond that I know to be the hardest substance for now.
hamidat
I thought I replied to this already. My apologies for the delay. Diamonds while very hard are not the hardest material on Earth. There is boron nitride but out of the 4 forms it can take it is the Wurtzite form (w-BN) that is harder than diamond.
Jallal
Next is Lonsdaleite which is also called hexagonal diamond because of its crystal structure but it is an allotrope of carbon with a hexagonal lattice. the lattice structure is packed even more closely than that of diamonds making Lonsdaleite 58% harder than diamond
Jallal
Then there's fullerene which is also an allotrope of carbon whose molecule consists of carbon atoms connected by single and double bonds so as to form a closed or partially closed mesh was fused rings of 5 to 7 atoms
Jallal
the molecule may be a hollow sphere an ellipsoid a tube are many other shapes and sizes. graphene which is a flat mesh of regular hexagonal rings can be seen as an extreme member of the family. because of their typical soccer balls like shape there are more commonly referred to as buckyballs.
Jallal
fullerenes which were discovered by accident greatly expanded known allotropes of carbon. this discovery gave rise to carbon nanotubes which are even harder than diamonds. each nanotubes is between 2 and 4 nanometers yeah it is incredibly strong and tough. weighing only 10% of the weight of steel
Jallal
but has hundreds of times the strength of steel
Jallal
then there is graphing which is a hexagonal carbon lattice that's only a single atom thick which is arguably the most revolutionary material to be developed and utilize in 21st century. the basic structural element of graphene are carbon nanotubes. in proportion to its thickness it is the strongest
Jallal
material known
Jallal
then there is beta carbon nitride which is a super hard material predicted to to have a hardness equal or above diamond.
Jallal
Thanks,but I have to go and research more to know better.
hamidat
lastly there is linear acetylenic carbon also called carbyne which is also an allotrope of carbon that has a chemical structure as a repeating chain with alternating single and triple bonds. it would thus be the ultimate member of the polyyne family.
Jallal
T
hamidat
the this polymeric carbyne is a considerable interest in Android technology as its Young's modulus is 32.7 TPa which is 40 times that of a diamond.
Jallal
I thought amongst the allotropes of carbon,diamond is octahedral and graphite is hexagonal?
hamidat
carbyne chains have been claimed to be the strongest material known for density. calculations indicate that carbyne's specific tensile strength beats graphene, carbon nanotubes, and diamond.
Jallal
There you have it Rahim
Jallal
So far so good, you have mentioned about 6 to 7 other compounds that are harder than diamond, are these real?
hamidat
yes they are. I would never make up lies just to sound smart. please check them yourself as it's never good to just take someone's word without doing your own research
Jallal
there are other materials too but they are disputable and upon further testing on them they proved to fall short
Jallal
No that's not what I mean.
hamidat
hamidat
the allotropes of carbon, diamond is tetrahedral lattice and graphite is bonded l together in sheets of a hexagonal lattice.
Jallal
I'm happy to help anytime I can. also what did you mean that's not what you meant? I'd like to fully answer your questions to your content
Jallal
Now I no better, thanks.
hamidat
you're welcome and anytime
Jallal
Sorry it was not meant for you,I was answering another question .
hamidat
okay Sir
hamidat
I can't reply through the other side,it filled up
hamidat
you can just create a new thread
Jallal
Diamond
Its
Diamond, while still one of the hardest substances, it has lost its top spot thanks to new discoveries
Jallal
I wish someone had more questions for me to answer. I like helping others and I love knowledge. Please everyone ask away no matter how trivial. Any question is always a good question. it's much better to be inquisitive than silent.
And I like asking people questions, so wait and collect yours.
hamidat
How can a mixture of petroleum be separated from kerosene?, which process is called the "Haber process", How is methane prepared laboratoryly.Thank u
hamidat
An organic compound decolorized acidified KMnO4 solution but failed to react with ammonical silver nitrate solution. the organic compound is likely to be?
Faith
hamidat. mixtures of two miscible liquids having a difference in their boiling points more than 25°C can be separated by the method of distillation.
Jallal
a mixture of kerosene in petroleum is taken in the distillation flask with a thermometer fit it in. you also need a beaker a water condenser in a Bunsen burner. once you have the apparatus set up then start to heat the mixture slowly. the thermometer should be watched simultaneously.
Jallal
kerosene will vaporize and condense in the water condenser. the condensed kerosene is collected from the condenser outlet whereas the petroleum is left behind and distillation flask.
Jallal
missing is prepared and laboratory by the protonation of methyl lithium and methyl magnesium iodide
Jallal
I'm not sure what you meant when you said which process is called the haber process. but I can say that the hub Haber-Bosch process is an artificial nitrogen fixation process and is the main industrial procedure for the production of ammonia today.
Jallal
the process converts atmospheric nitrogen (N2) to ammonia (NH3) buy a reaction with hydrogen (H2) using a metal catalyst under high temperatures and pressures.
Jallal
methane* is produced buy protonation of methyl lithium and muscle magnesium iodide. please excuse the typos
Jallal
ok I wanted to confirm because am having contradiction between fractional distillation and distillation itself.
hamidat
Jallal
ok well I'll always be happy to assist
Jallal
The reason why I ask for the Haber process is because some one told me is a process where hydrogen and nitrogen react to give ammonia and I was not sure.
hamidat
For methane, it is the laboratory preparation that am asking for.
hamidat
I see I gave you the laboratory synthesis but I think what you're looking for really is the industrial route synthesis. am I correct?
Jallal
You see,for distillation it has to do with two immiscible liquids so I normally misuse it for fractional distillation.
hamidat
The Haber process equation is : N2 + 3H2 ---> 2NH3 ∆H°=-91.8 kJ/mol
Jallal
Oh the one you gave above is the laboratory preparation/synthesis?
hamidat
yes, the one I gave was the laboratory synthesis not the industrial process I think that's what you we're looking for. I'll explain it right now
Jallal
Yes I have seen something like that: N2+3H2 _2NH3
hamidat
Sorry for the misunderstanding
hamidat
I only wish all the symbols could be displayed in the equation to avoid any confusion
Jallal
no worries. I like kitchen concepts
Jallal
Like seriously even I used to have that problem of symbols
hamidat
Methane (CH4) is one carbon in four atoms of hydrogen. it is a group 14 hydroid in the simplest alkane and is the main constituent of natural gas. through its relative abundance on Earth it is an attractive fuel however trying to capture and store it poses it's challenges due to its gaseous state
Jallal
under normal conditions for temperature and pressure.
Jallal
nothing is a tetrahedral molecule with four equivalent C-H bonds. it's electronic structure is described by four bonding molecular orbitals resulting from the overlap of the valence orbitals on C and H.
Jallal
it is also a component of petroleum gas right?
hamidat
at room temperature and standard pressure methane is a colorless odorless gas. The familiar smell of natural gas as used in homes is a chief with the addition of an odorant usually blends containing tert-butythoil as a safety measure.
Jallal
no it is a component of natural gas not petroleum gas
Jallal
OK
hamidat
nothing has a boiling point of -164 °C (-257.8 °F) at a pressure of 1 atmosphere. as a gas it is flammable over a range of concentrations (5.4-17%) in air at standard pressure.
Jallal
solid methane exist currently in 9 known modifications. cooling Messina normal pressure results in the formation of methane I. this substance crystallizes in the cubic system (space group Fm3m). the positions of the hydrogen atoms are not fixed in methane I. i.e. methane molecules may rotate freely.
Jallal
therefore it is a plastic Crystal
Jallal
the primary chemical reactions in methane or combustion, steam reforming to syngas and halogenation. in general medicine reactions are difficult to control.
Jallal
OK am with you
hamidat
hamidat
yes halogenation is a chemical reaction that involves the addition of one or more halogens to a compound or material
Jallal
okay
hamidat
I hope you're right because I don't feel blessed but it's my nature to help in any way I can
Jallal
there are different types of halogenation of organic compounds by reaction type so you must be mindful of that. there are free radical halogenation, ketone halogenation, electrophilic halogenation, and halogen addition reaction. the structure of the substrate is one factor that determine the pathway
Jallal
okay now that we have all that information out of the way we are going to now move on to the industrial synthesis
Jallal
You don't talk like that because the Lord has so many ways of blessing people, you don't know what you have now until you lose it.So ways feel blessed okay
hamidat
You don't talk like that because the Lord has so many ways of blessing people, you don't know what you have now until you lose it.So always feel blessed okay
hamidat
okay
hamidat
all I have is my knowledge and my brain. I think about it everyday about what I have and while not much at all things could be magnitudes worse so you're right I should be happy with I currently have. maybe fate will smile down on me one day. thanks for the pep talk
Jallal
So are you still in secondary school preparing to write WAEC?
hamidat
no I'm finished with my university studies where I majored in the Sciences. I just love to keep expanding my knowledge
Jallal
No Wonder you sound different from normal school student
hamidat
now let's begin the industrial process. there is little incentive to produce methane industrially. methane is produced by hydrogenating carbon dioxide through the Sabatier process
Jallal
Alright
hamidat
the Sabatier process dissolve the reaction of hydrogen and carbon dioxide at elevated temperatures (optimally 300-400 °C) and pressures in the presence of a nickel catalyst to produce methane and water.
Jallal
okay
hamidat
Hello are you still there
hamidat
optimally ruthenium on alumina (aluminum oxide) make some more efficient catalyst. this process is described by the following exothermic reaction: CO2 + 4H2 ----> CH4 + 2H2O ∆H= -165.0 kJ/mol. above the arrow symbol there should be 400 °C and below it should say pressure
Jallal
sorry I had to talk to my family over something. don't worry I'll see this to the end and make sure you understand my explanation
Jallal
No problem sir,thanks for your time
hamidat
whether the CO2 methanation occurs by first associatively adsorbing an adatom hydrogen and forming oxygen intermediates before hydrogenation or dissociating and forming a carbonyl before being hydrogenated we are then given the next equation: CO + 3H2 ---> CH4 + H2O. ∆H= -206 kJ/mol
Jallal
CO methanation is believed to occur through a dissociative mechanism where the carbon oxygen bond is broken before hydrogenation with an associative mechanism only being observed at a high H2 concentrations
Jallal
messing is also a side product of the hydrogenation of carbon monoxide in the Fischer-Tropish process, which is practiced on a large scale to produce longer-chain molecules than methane
Jallal
the Fisher-Tropsch process involves a series of chemical reactions that produce a variety of hydrocarbons, ideally haven't formula (CnH2n+2). the more useful reactions produce alkanes as follows: (2n + 1) H2 + n CO ---> CnH2n+2 + n H2O
Jallal
okay but what do you mean by "The Fischer-Tropish" process
hamidat
where n is typically 10-20. the formation of methane (n=1) is unwanted. most of the alkanes produced tend to be straight-chain, suitable as diesel fuel. in addition to alkane formation, computing reactions give small amounts of alkenes, as well as alcohols and other oxygenated hydrocarbons.
Jallal
what I mean is that there are two ways to produce methane on an industrial scale. one is by hydrogenating carbon dioxide through the Sabatier process and the other as a side product of the Fischer-Tropsh process.
Jallal
as a side product of the hydrogenation of carbon monoxide in the Fisher-Tropsch process
Jallal
now I understand
hamidat
example of large-scale coal-to- methane gasification is the Great Plains Synfuels plant, in North Dakota as a way to develop abundant local resources of low-grade lignite, a resource that is otherwise difficult to transport for its weight, ash content, low calorific value and propensity
Jallal
just spontaneous combustion during storage and transport.
Jallal
power to methane is a technology that uses electrical power to produce hydrogen from water by electrolysis and uses the Sabatier reaction to combine hydrogen with carbon dioxide to produce methane.
Jallal
you see all these things are not in this secondary school textbooks that am using
hamidat
it depends on the books and authors of the books because I've seen academic books tremendously different from each other with completely different concepts
Jallal
also the edition and year of publication. my experience is from University. are yours from high school?
Jallal
it's through
hamidat
through?
Jallal
I'm almost done with my explanation. only about 5 sentences left to wrap it all up.
Jallal
Sorry what I meant is"true"
hamidat
okay sir
hamidat
also secondary school books compared to university school books offer much more information. they limit the amount of knowledge your exposed to deliberately so as you progress you learn more newer previously unknown concepts
Jallal
as of 2016 this is mostly under development not in large-scale use. theoretically, the process could be used as a buffer for excess and off-peak power generated by highly fluctuating wind generators and solar arrays.
Jallal
To be sincere, all what you have been teaching me is not there
hamidat
however, as currently very large amounts of natural gas are used in power plants to produce electric energy, the losses and efficiency are not acceptable.
Jallal
this ends the lesson
Jallal
you mean in your text book?
Jallal
Yes
hamidat
Faith. the answer is "an alkenes"
Jallal
could you please tell me the name of the book, author, and edition? if you can find the ISBN that would help me find it faster
Jallal
I answered. both your questions and Faith's. I went back to everything I wrote I apologise for all the typos
Jallal
Thanks so much Sir ,I have learnt a lot today. I really appreciate.
hamidat
you're always welcome. I enjoying teaching. if you ever have any other questions or need help please reach out anytime. although I'm not sure how one does that in this app
Jallal
Jallal
Essential chemistry, Odesina I .A.
hamidat
ISBN:978-8089-44-5.For edition he wrote first, second, third and fourth edition here .
hamidat
thanks Sir.
hamidat
my pleasure
Jallal
sir hope the ISBN appeared
hamidat
the ISBN didn't appear and it's proving difficult to find that book and author.
Jallal
Jallal
I tried sending it but it won't go through
hamidat
Jallal
Gibbs free energy continued
when ∆G>0, the process is endergonic and not spontaneous in the forward direction. instead it will proceed spontaneously in the reverse direction to make more starting materials
Jallal
when ∆G=0, the system is in equilibrium and the concentrations of the products and reactants will remain constant
Jallal
when the system is in equilibrium that means the forward reaction and the reverse reaction are occurring at the same rate
Jallal
Although ∆G is temperature dependent, it's generally okay to assume that the ∆H and ∆S values are independent of temperature as long as the reaction does not involve a phase change. that means that if we know ∆H and ∆S we can use those values to calculate ∆G at any temperature.
Jallal
calculating ∆H and ∆S can be done using tables of standard values among other methods
Jallal
when the process occurs under standard conditions (all gases at 1 bar pressure, all concentrations are 1 M, and T=25°C), we can also calculate ∆G using the standard free energy of formation, ∆fG°
Jallal
be sure to pay close attention two units when ∆G from ∆H and ∆S because ∆H is given in kJ/mol-reaction while ∆S is given as J/mol-reaction • K, which is a difference factor of 1000
Jallal
when is ∆G negative? the equation of ∆Gsystem depends on 3 values. using ∆Gsystem=∆Hsystem-T∆Ssystem, the temperature in this equation is always positive or zero because it has units of K there for the second term in our equation T∆Ssystem will always have the same sign as ∆Ssystem
Jallal
now we can make the following conclusions about when processes will have a negative ∆Gsystem
Jallal
when the process is exothermic (∆Hsystem < 0), and the entropy of the system increases (∆Ssystem > 0), the sign of ∆Gsystem is negative at all temperatures. thus the process is always spontaneous
Jallal
when the process is endothermic, ∆Hsystem > 0, and the entropy of the system decreases, ∆Ssystem < 0, the sign of ∆G is positive at all temperatures. thus the process is never spontaneous
Jallal
for other combinations of ∆Hsystem and ∆Ssystem, the spontaneity of a process depends on the temperature
Jallal
exothermic reactions (∆Hsystem < 0) that decrease the entropy of the system (∆Ssystem < 0) are spontaneous at low temperatures
Jallal
endothermic reactions (∆Hsystem > 0) The increased entropy of the system (∆Ssystem > 0) or spontaneous at high temperatures
Jallal
thermodynamics is also connected to concepts in other areas of chemistry for example, in chemical equilibrium we can relate ∆G with the equilibrium constant, K
Jallal
in electrochemistry, ∆G is related to the cell voltage, Ecell
Jallal
lastly depending on the signs of ∆H and ∆S, the spontaneity of a process can change at different temperatures
Jallal
if any part of this explanation of the concept of Gibbs free energy is not clear please let me know so I may clarify
Jallal
That is good my brother,continue.
hamidat
Jallal, I like the ways you answer questions, you always break it down to the simplest, I which I can get somebody like you that will be teaching me.
hamidat
I could have broken it down further by giving detailed sample problems but stopped short assuming everyone understood as I wasn't receiving feedback. if you'd like I'd be happy to teach you whenever you like or need. we could setup email correspondence or video chats
Jallal
OK whenever am ready I will let you know
hamidat
know what?
Jallal
I can skip to the very crucial process instead of giving a complete breakdown of how the process works
Jallal
You see am preparing for WAEC and I am a little nervous
hamidat
just keep studying and reviewing when you're not 100% on and go in feeling completely confident
Jallal
sorry for the typos
Jallal
let's continue
Jallal
Thank you so much,God will continue to bless you
hamidat
Why's Ph not good for consumption?
A given amount of gas occupies 10.0dm5 at 4atm and 273°C. The number of moles of the gas present is? [ Molar volume of gas at s.t.p= 22.4dm3]
you must use the Ideal Gas Law equation: pV=nRT, where p is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature. You have everything you need to calculate the answer you just need to do some algebra first to rearrange the equation to find n
Jallal
Jallal
for the future always remember that the pressure must be pascals. the volume must be converted to cubic meters, the gas constant R is 8.31441 J K^-1 mol^-1, the temperature must always be in Kelvin so if you are given degrees in Celsius make sure to add 273 to it
Jallal
solubility
Shehu
solubility
Abubakkar
yes tell me more on solubility
Shehu
solubility is the property of a solid, liquid, or a gaseous chemical substance called solute to dissolve in a solid, liquid or gaseous solvent. the solubility of a substance fundamentally depends on the physical and chemical properties of the solute and solvent as well as temperature, pressure and
Jallal
presence of other chemicals (including changes in pH) of the solution.
Jallal
the extent of the solubility of a substance in a specific solvent is measured as the saturation concentration, we're adding more solute does not increase the concentration of the solution and begins to precipitate the exorcism out of solute.
Jallal
precipitate of the excess amount of solute collects at the bottom in solid form
Jallal
this is because the solvent it's completely saturated you cannot dissolve any more solute
Jallal
the solvent most commonly used is water which is why it is also called the universal solvent as it can most readily mix with mostly anything
Jallal
excuse the few typos
Jallal
hi
Affum
welcome affum
Shehu
But Jallal,sometimes the pressures are given in:atm,mmHg, Newton per metre square. How will you know the right unit to use?
hamidat
that's why conversion formulas are for
Jallal
that's what*
Jallal
if pressure is given ATM younger convert ATM to Pascal all you would have to do is multiply the amount of ATM let's say 1 by 101325
Jallal
this one 101325 is it constant?
hamidat
yes 1 ATM is always equal to 101325 pascals at sea level at a temperature of 15°C
Jallal
Alright, Good morning
hamidat
But what if your given the pressure in Bars? the same concept still applies you always want to get pressure in pascals. 1 Bar = 100000 pascals
Jallal
okay
hamidat
now let's assume that the pressure is given in mmHg. 1 mmHg is equal to 133.3224 pascals
Jallal
find me if we are given pressure and Newton per square meter square meter is exactly equal to one pascal.
Jallal
let me rephrase that last one. we are given pressure and Newton per square meter then the pressure will be exactly 1 pascal. as one newton per square meter is exactly equal to 1 pascal
Jallal
how do u derive this fundamental constants
am not sure how
Shehu
do you have an idea
Shehu
no
Mugala
Bertram
could you elaborate a little more on your question?
Jallal
or reword it perhaps. I think I understand what you're trying to ask but the wording of the question makes it confusing
Jallal
what fundamental constants?
Ruth
you see Bertran. if you can do a little more explaining on what you are trying to have answered there wouldn't be so much confusion and you'd most likely get your answer your searching for
Jallal
Bertram*
Jallal
this value would be a little hard to understand so I thought you should know how it is derived
Bertram
I need a deeper explanation to this value
Bertram
you're still being very ambiguous. please tell me what fundamental constant you are referring to.
Jallal
am asking this question under fundamental physical constant
Bertram
ok how do u derive the value of Avogadro's number without cramming
Bertram
fundamental physical constants are dimensionless and cannot be derived and have to be measured.
Jallal
dimensionless quantities are obtained as ratios of quantities that are not dimensionless
Jallal
if you want to understand better then I suggest you read up on "dimensional analysis", "dimensionless quantity", and "dimensionless physical constant"
Jallal
Fundamental constants are stationary They can't be created they are just there like current... Always in ampere and others Jallal I like ur knowledge can we be friends?
Its
isnt there some debate as the as to whether or not the constants do actually change?
Dale
of course we can be friends. I like to have intellectual conversations and people alike.
Jallal
there's always a debate about everything as not everyone can always agree on something. this is very common among scientists. however, for the sake of your question since the universe is always heading in the direction of entropy let's assume that some constants may change given a million years
Jallal
of course this is unfounded and I don't believe that but I'm just trying to indulge you
Jallal
what is an atom
An atom is the smallest indivisible particle of an element that is capable of independent existence
akinboboye
That's conventional thinking since the Greeks and our current teaching, but it's been discovered that atoms are made up of even smaller subatomic particles called "quarks". Until fully understood let's stick with the current knowledge that an atom is the smallest unit of mass being indivisible
Jallal
definition of ions
Salman
an ion is an atom or molecule that has a net electrical charge. the charge of the electron atom as negative and is equal and opposite to that of the proton that item which is positive. the net charge of an ion is non-zero.
Jallal
this is due to the total number of electrons being on equal to its total number of protons. a cation is a positively charged ion with fewer electrons than protons while an anion is negatively charged with more electrons and protons.
Jallal
because of their opposite electric charges cations and anions attract each other and readily form ionic compounds.
Jallal
thanks
Salman
so please who can throw more light on acids and base for me
Shehu
an acid is a molecule or ion capable of donating a proton (hydrogen ion H+) it is a substance that increases the concentration of hydronium ions (H3O+) when added to water or decreases the hydroxide concentration water.
Jallal
how separating acid to gas
Abubakkar
a base is a proton acceptor and it's a substance that dissociates in water to form hydroxide ions (OH-). thus the base decreases the aqueous hydronium concentration in water and increases aqueous hydroxide concentration in water.
Jallal
also a reaction between an acid with a base is called a neutralization reaction and the products of the reaction are salt and water and not an acid or base
Jallal
is the smallest particle of elements
Abubakkar
separating acid to gas is there a process called amine gas treating also called acid gas removal. since many different amines can be used in the process each process is slightly different depending on which amine to use.
Jallal
can I get some example of concentrated acid
Shehu
hydrochloric acid (HCl) it can come in diluted forms which you can apply on your hands (obviously not recommended) but that's to show it's concentration then there's highly concentrated HCl which will instantly burn/melt your skin
Jallal
If you want the strongest most concentrated acid there is then that's hydrogen fluoride (HF) now that is some very nasty stuff. even with proper equipment it can still be extremely dangerous to handle
Jallal
thank you jallal
Shehu
anytime
Jallal
jallal am going to be writing an exam on chemistry can you tell me some important stuff in chemistry
Shehu
I need a little more information than that. you see there's general chemistry, organic chemistry, nonorganic chemistry, analytical chemistry, biochemistry. which subject is it and what exactly will be your topic?
Jallal
I'm not really sure what you mean by important stuff so I give general ideas and principals. ranging from basic fundamentals to more in depth knowledge
Jallal
chemistry is a branch of science that studies matter and change. first chemistry deals with the study of the composition and the properties of matter then chemistry deals with change or how these substances evolve when submitted to certain conditions or how one substance changes or reacts while
Jallal
interacting with a different substance
Jallal
everything is chemistry from the chemicals in our foods to the air we breathe even to the medicine we use. everyday modern life all involves mixture of chemistry
Jallal
chemistry is also known as the central science without chemistry you wouldn't have the physical sciences or life sciences such as biology or applied sciences like engineering. in essence all sciences are glued together by chemistry
Jallal
an atom is defined as the basic unit of a chemical element however we now know that atoms are made of smaller particles called subatomic particles known as protons electrons and neutrons. protons and neutrons are not fundamental particles they're made of quarks. electrons are fundamental particles
Jallal
and they are not made of anything smaller
Jallal
a molecule is a group of atoms bound together which is the next step of chemical complexity. molecules represent the basic unit of a chemical compound
Jallal
there are three basic types of chemical compounds which have different bonding properties the difference is the force that holds together the atoms
Jallal
neutral molecules or compounds in nature or held together by covalent bonds. covalent bonds generally occur between two nonmetal atoms with share pairs of electrons or bonding pairs
Jallal
then there are ionic compounds where atoms are in ionic form which is to say charged and are held together by ionic forces which give rise to large networks of oppositely charged ions. ionic bonds occur between metals and nonmetals. one ionic compound example is sodium chloride also known as salt
Jallal
then there are extended networks of atoms formed between one or more types of metal atoms which are called metallic bonds
Jallal
chemistry studies changes in matter thus a chemical reaction is a process in which one set of chemical compounds are transformed into another. this occurs when there is an interaction between the compounds in which some initial bonds are broken and some new bonds are formed.
Jallal
this happens because the energy holding the new bonds together is higher than the energy that held the initial bonds. this is what is known as a thermodynamically favored process. favorable thermodynamics is the most fundamental step that leads to compounds to react with each other
Jallal
another important factor that allows compounds to react with each other is known as reaction kinetics
Jallal
there is also something known as chirality which is a geometric property of certain molecules. molecule is said to be chiral when its mirror image is not superimposable to the molecule itself.
Jallal
essentially chirality is symmetrical mirror image of a molecule. this can also be explained through enantiomers. however the origin of chirality is still unknown and debatable as to why it came to exist in the first place but they do serve important biological functions. many medicines use chirality
Jallal
then there acids and bases. an acid is a compound such as hydrochloric acid (HCl) that is able to release a hydrogen cation or proton (H+). basis such as sodium hydroxide (NaOH) can catch protons water given rise to hydroxide anions.
Jallal
basically an acid is a substance that accepts alone pair of electrons and a base is a substance that donates a lone pair of electrons. relative acidity or basicity of solutions are mixtures is measured using a logarithmic scale called the pH scale which goes from 0 to 14. 7 is considered neutral
Jallal
anyting below 7 is considered acidic with 0 being the most acidic. anything above 7 is considered basic with 14 being the most basic.
Jallal
stoichiometry is a way of measuring or determining the amount of each substance that is involved in a reaction (reactants), and the amount of products that are generated. basically this is just making both sides of the reaction, the reactants and the products equal to each other so the reaction to
Jallal
proceed
Jallal
next comes oxidation and reduction. redox processes are a type of chemical reaction in which one of the reacting compounds gets oxidized and the other gets reduced. a redox reaction involves the transfer of electrons. when a compound or atom loses electrons it is oxidized.
Jallal
when a compound or atom gains electrons it is reduced
Jallal
the most common example of a redox process is the rusting of iron. when oxygen reacts with iron it produces iron oxide. the new oxidation state of iron is + 3 iron has lost three electrons therefore it is oxidized.
Jallal
on the other hand the new oxidation state of oxygen is -2 therefore each oxygen atom has gained two electrons becoming reduced
Jallal
then there is also radioactive decay or radioactivity. this a the process in which an unstable nucleus loses energy by the emission of radiation in the form of a particle. not all atoms that exist or stable. one of these unstable atoms decay they release energy in the form of particles
Jallal
this is what we call radiation. when this process takes place a new nucleus is formed and therefore also a new atom. the new atom can also be unstable and it can keep releasing radiation until it turns into a stable atom which no longer emits energy as radiation.
Jallal
if you would like me to discuss and explain other areas of chemistry please let me know I will be more than happy to
Jallal
thank you jallal
Shehu
any more important things to know
Shehu
there are lots of important things. I can write them up for hours and still have more to say which I don't mind. how much more or detail do you require? in the meantime I'll just keep typing up other important areas of chemistry.
Jallal
balancing equation,Gibbs free energy
Shehu
sure thing. I just need to type protocol development on a clinical trial and send it to my employer. please give me a few moments to finish the study design and guidelines
Jallal
in what other form do we extract zinc apart from blende?
miriam
a chemical equation is the symbolic representation of a chemical reaction. the reactant entities are on the left hand side while the product entities are on the right hand side.
Jallal
because of the law of conservation of mass dictates that the quantity of each element does not change in a chemical reaction and the law of conservation of charge also states that the charge is conserved in a chemical reaction therefore each side of the chemical equation must represent the same
Jallal
quantity of any particular element also the same charge must be present on both sides of the balanced equation. this is where stoichiometric comes into play which is the calculation of reactants and products in chemical reactions
Jallal
balancing a chemical formula for a simple chemical reaction can be easily done by trial-and-error however more complex chemical equations can be solved using a system of linear equations.
Jallal
when balancing equations one should use the smallest whole-number coefficient. if a fractional coefficient exists then multiply every coefficient with the smallest number required to make them whole which is typically the denominator of the fractional coefficient
Jallal
an example of one balanced equation is: 2 HCl + 2 Na --> 2 NaCl + H^2. the 2 on the last hydrogen is supposed to be a subscript but I don't have that symbol on my phone
Jallal
an example of one balanced equation is: 2 HCl + 2 Na --> 2 NaCl + H^2.
Jallal
if if there is no coefficient in front of the chemical formula then the coefficient is automatically 1
Jallal
another example of a balanced equation is CH4 + 2O2 --> CO2 + 2H2O
Jallal
the 2 after the first oxygen on the left side it's supposed to be a subscript also the 2 after the oxygen on the right side is also a subscript same goes for the 2 in H2O
Jallal
the stoichiometric ratio free agent is the optimum amount when all of the reagent consumed, there is no deficiency of the reagent, and there is no excess of their reagent
Jallal
regardless of whether or not all the atoms are actually involved in a reaction both sides of the formula, the reactant side and the product side must be equal
Jallal
also different elements have different atomic mass so as a collection of single atoms molecules have a definite molar mass measured with the unit mole also known as Avogadro's constant. thus to calculate the stokke allometry by mass the number of molecules required for each reactant is expressed
Jallal
in moles and multiplied by the molar mass of each to give the mass of each reactant per mole of reaction. the mass ratios can be calculated by dividing each why the total in the whole reaction.
Jallal
stoichiometric is not only used to balance equations but also used in conversions such as converting from grams to moles using molar mass as a conversion factor or from grams to milliliters using density. for example to find the amount of NaCl (sodium chloride) in 2.00 g, you would do the following.
Jallal
2.00 g NaCl/58.44 g NaCl mol^-1= 0.034 mol
Jallal
stokke allometry is also used to balance chemical equations known as reaction stoichiometry to determine molar proportion. for example 2 diatomic gases, hydrogen oxygen, can combine to form a liquid, water, in an exothermic reaction shown by the following 2 H^2 + O^2 --> 2 H2O
Jallal
stoichiometry can also be used to find the quantity of a product yielded by a reaction. if a piece of solid copper (Cu) or added to an aqueous solution of silver nitrate (AgNO3), the silver (AG) would be replaced in a single displacement reaction forming aqueous copper (II) nitrate (Cu(NO3)2) and
Jallal
solid silver. how much silver is produced if 16.00 grams of Cu is added to the solution of excess silver nitrate?
Jallal
the following steps would be used: 1. write and balance the equation. 2. Mass to moles: convert grams of Cu 2 moles of Cu. 3. Mole ratio: convert moles of Cu to moles of Ag produced. 4. Mole to mass: convert moles of Ag to grams of Ag produced
Jallal
the complete balanced equation would be: Cu + 2 AgNO3 ---> Cu(NO3)2 + 2 Ag
Jallal
I think I went into more depth than you wanted. let me give a simplified version of balancing equations
Jallal
chemical equations are used to describe the rearrangement of atoms and electrons during a chemical reaction.
Jallal
the atoms can be neither created nor destroyed and always react in fixed proportions each side of the equation must contain the same number of each kind of atom. this is called a balanced equation
Jallal
example: for the reaction of hydrogen and oxygen to give water, H2 + O2 ---> H2O
Jallal
equation is unbalanced. there are two oxygens on the reactant side, only one on the product side. to balance it, the number of product water molecules must be increased to 2, and then the number of reactant H2 molecules must also be increased to 2.
Jallal
this provides the balanced equation: 2H2 + O2 ---> 2H2O
Jallal
you can also visually draw these two equations to show you the unbalanced equation and the balanced equation.
Jallal
that concludes balanced equations. now on to Gibbs free energy
Jallal
Gibbs free energy is part of thermodynamics it is also known as free enthalpy which is also a thermodynamic potential that can be used to calculate the maximum of reversible work that may be performed by thermodynamic system at a constant temperature and pressure.
Jallal
the Gibbs free energy equation is: (∆G°=∆H-T∆S°), and is measured in joules
Jallal
∆G° is Gibbs free energy. ∆H° is change in enthalpy. ∆S° is the change in entropy. T is the temperature always in Kelvin at 298.15 K. the second law of thermodynamics helps us determine whether a process will be spontaneous and using changes in Gibbs free energy to predict whether a reaction will be
Jallal
genius in the forward or reverse direction or whether it is at equilibrium
Jallal
the second law of thermodynamics says that entropy of the universe always increases for a spontaneous process: ∆Suniverse=∆Ssystem + ∆Ssurroundings > 0
Jallal
at constant temperature and pressure the change in Gibbs free energy is defined as ∆G=∆H-T∆S
Jallal
when ∆G is negative a process will proceed spontaneously and is referred to as exergonic
Jallal
the spontaneity other process can depend on the temperature
Jallal
in chemistry a spontaneous process is one that occurs without that diction of external energy. spontaneous process may take place slowly or quickly because spontaneity is not related to kinetics or reaction rate.
Jallal
a spontaneous processes can be exothermic or endothermic. which is to say that spontaneity is not necessarily related to the enthalpy change of a process, ∆H
Jallal
we can determine if a process will occur spontaneously by using the second law of thermodynamics which states any spontaneous process must increase the entropy in the universe. this can be expressed mathematically as follows: ∆Suniverse=∆Ssystem + ∆Ssurroundings > 0 for a spontaneous process
Jallal
to determine the change in entropy and spontaneity we use Gibbs free energy equation shown before. the symbol G has typically units of kJ/mol-rxn also known as kilojoules over mole of reaction
Jallal
when using Gibbs free energy to determine the spontaneity of a process we are only concerned with the changes in G rather than its absolute value. the change in Gibbs free energy for a process is thus written as ∆G, which is the difference between Gfinal, the Gibbs free energy of the products
Jallal
and Ginitial, the Gibbs free energy of the reactants. ∆G=Gfinal-Ginitial
Jallal
the equation ∆G=∆H-T∆S allows us to determine the change in Gibbs free energy using the enthalpy change ∆H and the entropy change ∆S. we can use ∆G to determine whether a reaction is spontaneous in the forward direction backward direction or if the reaction is at equilibrium
Jallal
when ∆G<0, the process is exergonic and will proceed spontaneously in the forward direction to form more products
Jallal
What is rightful definition of element
an element is the group of (vertical columns) of the periodic table exhibit similar chemical behaviour.
Barnabas
okay
angela
any other information
Salman
a chemical element is a species of atom having the same number of protons and it's atomic nuclei
Jallal
for example let's use oxygen the atomic number of oxygen is 8 so the element oxygen describes all atoms which have 8 protons
Jallal
Jallal
in*
Jallal
is alkanes a saturated hydrocarbon?
yup
it's saturated cos it has single bonds
yh....because they don't undergo additional reactions which hydrogen and other atoms can add across the carbon-carbon or triple bond
patience
and me...I'm I wrong?
patience