# 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.

what is variations in raman spectra for nanomaterials
I only see partial conversation and what's the question here!
what about nanotechnology for water purification
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
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 did you get the value of 2000N.What calculations are needed to arrive at it
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Good
What makes metals better to use as wires than non-metals? (please link to bonding type)??? HELP