18.5 Occurrence, preparation, and compounds of hydrogen  (Page 5/9)

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${\text{2H}}_{2}\text{S}\left(g\right)+{\text{O}}_{2}\left(g\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{2S}\left(s\right)+{\text{2H}}_{2}\text{O}\left(l\right)$

This oxidation process leads to the removal of the hydrogen sulfide found in many sources of natural gas. The deposits of sulfur in volcanic regions may be the result of the oxidation of H 2 S present in volcanic gases.

Hydrogen sulfide is a weak diprotic acid that dissolves in water to form hydrosulfuric acid. The acid ionizes in two stages, yielding hydrogen sulfide ions, HS , in the first stage and sulfide ions, S 2− , in the second. Since hydrogen sulfide is a weak acid, aqueous solutions of soluble sulfides and hydrogen sulfides are basic:

${\text{S}}^{2-}\left(aq\right)+{\text{H}}_{2}\text{O}\left(l\right)\phantom{\rule{0.2em}{0ex}}⇌\phantom{\rule{0.2em}{0ex}}{\text{HS}}^{\text{−}}\left(aq\right)+{\text{OH}}^{\text{−}}\left(aq\right)$
${\text{HS}}^{\text{−}}\left(aq\right)+{\text{H}}_{2}\text{O}\left(l\right)\phantom{\rule{0.2em}{0ex}}⇌\phantom{\rule{0.2em}{0ex}}{\text{H}}_{2}\text{S}\left(g\right)+{\text{OH}}^{\text{−}}\left(aq\right)$

Halogen hydrogen compounds

Binary compounds containing only hydrogen and a halogen are hydrogen halides . At room temperature, the pure hydrogen halides HF, HCl, HBr, and HI are gases.

In general, it is possible to prepare the halides by the general techniques used to prepare other acids. Fluorine, chlorine, and bromine react directly with hydrogen to form the respective hydrogen halide. This is a commercially important reaction for preparing hydrogen chloride and hydrogen bromide.

The acid-base reaction between a nonvolatile strong acid and a metal halide will yield a hydrogen halide. The escape of the gaseous hydrogen halide drives the reaction to completion. For example, the usual method of preparing hydrogen fluoride is by heating a mixture of calcium fluoride, CaF 2 , and concentrated sulfuric acid:

${\text{CaF}}_{2}\left(s\right)+{\text{H}}_{2}{\text{SO}}_{4}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{CaSO}}_{4}\left(s\right)+\text{2HF}\left(g\right)$

Gaseous hydrogen fluoride is also a by-product in the preparation of phosphate fertilizers by the reaction of fluoroapatite, Ca 5 (PO 4 ) 3 F, with sulfuric acid. The reaction of concentrated sulfuric acid with a chloride salt produces hydrogen chloride both commercially and in the laboratory.

In most cases, sodium chloride is the chloride of choice because it is the least expensive chloride. Hydrogen bromide and hydrogen iodide cannot be prepared using sulfuric acid because this acid is an oxidizing agent capable of oxidizing both bromide and iodide. However, it is possible to prepare both hydrogen bromide and hydrogen iodide using an acid such as phosphoric acid because it is a weaker oxidizing agent. For example:

${\text{H}}_{3}{\text{PO}}_{4}\left(l\right)+{\text{Br}}^{\text{−}}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{HBr}\left(g\right)+{\text{H}}_{2}{\text{PO}}_{4}{}^{\text{−}}\left(aq\right)$

All of the hydrogen halides are very soluble in water, forming hydrohalic acids. With the exception of hydrogen fluoride, which has a strong hydrogen-fluoride bond, they are strong acids. Reactions of hydrohalic acids with metals, metal hydroxides, oxides, or carbonates produce salts of the halides. Most chloride salts are soluble in water. AgCl, PbCl 2 , and Hg 2 Cl 2 are the commonly encountered exceptions.

The halide ions give the substances the properties associated with X ( aq ). The heavier halide ions (Cl , Br , and I ) can act as reducing agents, and the lighter halogens or other oxidizing agents will oxidize them:

${\text{Cl}}_{2}\left(aq\right)+{\text{2e}}^{-}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{2Cl}}^{\text{−}}\left(aq\right)\phantom{\rule{5em}{0ex}}E\text{°}=1.36\phantom{\rule{0.2em}{0ex}}\text{V}$
${\text{Br}}_{2}\left(aq\right)+{\text{2e}}^{-}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{2Br}}^{\text{−}}\left(aq\right)\phantom{\rule{5em}{0ex}}E\text{°}=1.09\phantom{\rule{0.2em}{0ex}}\text{V}$
${\text{I}}_{2}\left(aq\right)+{\text{2e}}^{-}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{2I}}^{\text{−}}\left(aq\right)\phantom{\rule{5em}{0ex}}E\text{°}=0.54\phantom{\rule{0.2em}{0ex}}\text{V}$

For example, bromine oxidizes iodine:

${\text{Br}}_{2}\left(aq\right)+\text{2HI}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{2HBr}\left(aq\right)+{\text{I}}_{2}\left(aq\right)\phantom{\rule{5em}{0ex}}E\text{°}=0.55\phantom{\rule{0.2em}{0ex}}\text{V}$

how do u derive this fundamental constants
am not sure how
Shehu
do you have an idea
Shehu
no
Mugala
that's why am asking
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
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
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
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
how does metal looses electron
By oxidation and reduction
hamidat
by oxidation loss
Official
An acid is a proton donor.
what is an acid
an acid is a substance when dissolved in water produces hydrogen ion or hydroxonium ion
hamidat
good
Mudassir
thanks
hamidat
is a substance which dissolves in water to produce hydrogen ions as the only positively charged ions
Kwagala
what is ionic bonding
It involves the transferring of electron from a metal to a non mental
hamidat
that's right
Edward
bonding between a metal and a non metal
miriam
calculate the hydrogen ion concentration of the solution when pH=5
What is thermodynamics
what is the meaning this word twentieth
dhu
Is the branch of physics that deal with heat and temperature and their relation to work, energy and properties of matter
Edward
There are no topics on hydrocarbons
they are there please check under organic chemistry in the contents.
Kwagala
its not making sense to me I still don't understand
How and why
Betrice
yes
megan
we need diagram for easy going and understand
serah
How can we easily differentiate between the 5 gas laws
first amd foremist me i only know 3 gas laws, so please list them here
Kwagala
the gas laws i know include pressure law boyles law charles law i differentiate these with this formular big take classy pork pigs. viral i read thus as 1 big classy pigs take pork viral big.....take means in boyles law,temp is constant clasy.....prk mns in chrls lw, press cons
Kwagala
classy.....pork means in charles law pressure is constant pigs.....viral means, in pressure law volume is kept constsng ,the rest is the same boyles states that vol of a gas is inversely prop to volume keeping temp constant charles law, state vol of a gas is directly prop to temp keepn pressure cns
Kwagala
how many carbon is present in alkene
it's the carbon to carbon being double bonded to each other that makes it an alkene, not the amount of carbon itself. ex: C=C, C=C=C. both are alkenes.
Phill
I need more light on alkene
chidera
an alkene is a hydrocarbon, you can find this under the sub topic of organic chemistry in this textbook, check it out please,but before you know about alkenes you should first know about alkanes, alkanes are saturated and dnt easily react while alkenes have double bonds and can react .
Kwagala
other usefullness of hydrogen apart from this, it is colourless, odourless and tasteless
it is neutral to litmus paper, it is insoluble in water
hamidat