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

 Page 2 / 10

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

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.

#### Questions & Answers

so some one know about replacing silicon atom with phosphorous in semiconductors device?
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
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
how did you get the value of 2000N.What calculations are needed to arrive at it
Privacy Information Security Software Version 1.1a
Good
What makes metals better to use as wires than non-metals? (please link to bonding type)??? HELP