# 0.8 Reactions in aqueous solutions  (Page 2/10)

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${\mathrm{K}}_{2}{\mathrm{SO}}_{4}\mathrm{\left(s\right)}\to 2{\mathrm{K}}^{+}\mathrm{\left(aq\right)}+\mathrm{SO}{}_{4}^{2-}\mathrm{\left(aq\right)}$

Remember that molecular substances (e.g. covalent compounds) may also dissolve, but most will not form ions. One example is sugar.

${\mathrm{C}}_{6}{\mathrm{H}}_{12}{\mathrm{O}}_{6}\mathrm{\left(s\right)}⇌{\mathrm{C}}_{6}{\mathrm{H}}_{12}{\mathrm{O}}_{6}\mathrm{\left(aq\right)}$

There are exceptions to this and some molecular substances will form ions when they dissolve. Hydrogen chloride for example can ionise to form hydrogen and chloride ions.

$\mathrm{HCl\left(g\right)}\to {\mathrm{H}}^{+}\mathrm{\left(aq\right)}+{\mathrm{Cl}}^{-}\mathrm{\left(aq\right)}$

## Interesting fact

The ability of ionic compounds to dissolve in water is extremely important in the human body! The body is made up of cells , each of which is surrounded by a membrane . Dissolved ions are found inside and outside of body cells in different concentrations. Some of these ions are positive (e.g. ${\mathrm{Mg}}^{2+}$ ) and some are negative (e.g. ${\mathrm{Cl}}^{-}$ ). If there is a difference in the charge that is inside and outside the cell, then there is a potential difference across the cell membrane. This is called the membrane potential of the cell. The membrane potential acts like a battery and affects the movement of all charged substances across the membrane. Membrane potentials play a role in muscle functioning, digestion, excretion and in maintaining blood pH to name just a few. The movement of ions across the membrane can also be converted into an electric signal that can be transferred along neurons (nerve cells), which control body processes. If ionic substances were not able to dissociate in water, then none of these processes would be possible! It is also important to realise that our bodies can lose ions such as ${\mathrm{Na}}^{+}$ , ${\mathrm{K}}^{+}$ , ${\mathrm{Ca}}^{2+}$ , ${\mathrm{Mg}}^{2+}$ , and ${\mathrm{Cl}}^{-}$ , for example when we sweat during exercise. Sports drinks such as Lucozade and Powerade are designed to replace these lost ions so that the body's normal functioning is not affected.

Write a balanced equation to show how silver nitrate ( ${\mathrm{AgNO}}_{3}$ ) dissociates in water.

1. The cation is: ${\mathrm{Ag}}^{+}$ and the anion is: ${\mathrm{NO}}_{3}^{-}$
2. Since we know both the anion and the cation that silver nitrate dissociates into we can write the following equation:
${\mathrm{AgNO}}_{3}\mathrm{\left(s\right)}\to {\mathrm{Ag}}^{+}\mathrm{\left(aq\right)}+{\mathrm{NO}}_{3}^{-}\mathrm{\left(aq\right)}$

## Ions in solution

1. For each of the following, say whether the substance is ionic or molecular.
1. potassium nitrate ( $\mathrm{KNO}{}_{3}$ )
2. ethanol ( $\mathrm{C}{}_{2}\mathrm{H}{}_{5}\mathrm{OH}$ )
3. sucrose (a type of sugar) ( $\mathrm{C}{}_{12}\mathrm{H}{}_{22}\mathrm{O}{}_{11}$ )
4. sodium bromide ( $\mathrm{NaBr}$ )
2. Write a balanced equation to show how each of the following ionic compounds dissociate in water.
1. sodium sulphate ( $\mathrm{Na}{}_{2}\mathrm{SO}{}_{4}$ )
2. potassium bromide ( $\mathrm{KBr}$ )
3. potassium permanganate ( $\mathrm{KMnO}{}_{4}$ )
4. sodium phosphate ( $\mathrm{Na}{}_{3}\mathrm{PO}{}_{4}$ )

## Ions and water hardness

This section is not examinable and is included as an example of ions in aqueous solution.

Water hardness
Water hardness is a measure of the mineral content of water. Minerals are substances such as calcite, quartz and mica that occur naturally as a result of geological processes.

Hard water is water that has a high mineral content. Water that has a low mineral content is known as soft water . If water has a high mineral content, it usually contains high levels of metal ions, mainly calcium ( $\mathrm{Ca}$ ) and magnesium ( $\mathrm{Mg}$ ). The calcium enters the water from either ${\mathrm{CaCO}}_{3}$ (limestone or chalk) or from mineral deposits of ${\mathrm{CaSO}}_{4}$ . The main source of magnesium is a sedimentary rock called dolomite, ${\mathrm{CaMg\left(CO}}_{3}\mathrm{\right)}{}_{2}$ . Hard water may also contain other metals as well as bicarbonates and sulphates.

Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
what does nano mean?
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
how did you get the value of 2000N.What calculations are needed to arrive at it
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Berger describes sociologists as concerned with
What makes metals better to use as wires than non-metals? (please link to bonding type)??? HELP