# 0.8 Reactions in aqueous solutions  (Page 8/10)

 Page 8 / 10

Salts of carbonates, phosphates, oxalates, chromates and sulphides are generally insoluble.

## Testing for common anions in solution

It is also possible to carry out tests to determine which ions are present in a solution. You should try to do each of these tests in class.

## Test for a chloride

Prepare a solution of the unknown salt using distilled water and add a small amount of silver nitrate solution. If a white precipitate forms, the salt is either a chloride or a carbonate.

${\mathrm{Cl}}^{-}+{\mathrm{Ag}}^{+}+{\mathrm{NO}}_{3}^{-}\to \mathrm{AgCl}+{\mathrm{NO}}_{3}^{-}$
( $\mathrm{AgCl}$ is white precipitate)
${\mathrm{CO}}_{3}^{2-}+2{\mathrm{Ag}}^{+}+2{\mathrm{NO}}_{3}^{-}\to {\mathrm{Ag}}_{2}{\mathrm{CO}}_{3}+2{\mathrm{NO}}_{3}^{-}$
( ${\mathrm{Ag}}_{2}{\mathrm{CO}}_{3}$ is white precipitate)

The next step is to treat the precipitate with a small amount of concentrated nitric acid . If the precipitate remains unchanged, then the salt is a chloride. If carbon dioxide is formed, and the precipitate disappears, the salt is a carbonate.

$\mathrm{AgCl}+{\mathrm{HNO}}_{3}\to$ (no reaction; precipitate is unchanged)

${\mathrm{Ag}}_{2}{\mathrm{CO}}_{3}+2{\mathrm{HNO}}_{3}\to 2{\mathrm{AgNO}}_{3}+{\mathrm{H}}_{2}\mathrm{O}+{\mathrm{CO}}_{2}$ (precipitate disappears)

## Test for a sulphate

Add a small amount of barium chloride solution to a solution of the test salt. If a white precipitate forms, the salt is either a sulphate or a carbonate.

${\mathrm{SO}}_{4}^{2-}+{\mathrm{Ba}}^{2+}+{\mathrm{Cl}}^{-}\to {\mathrm{BaSO}}_{4}+{\mathrm{Cl}}^{-}$ ( ${\mathrm{BaSO}}_{4}$ is a white precipitate)

${\mathrm{CO}}_{3}^{2-}+{\mathrm{Ba}}^{2+}+{\mathrm{Cl}}^{-}\to {\mathrm{BaCO}}_{3}+{\mathrm{Cl}}^{-}$ ( ${\mathrm{BaCO}}_{3}$ is a white precipitate)

If the precipitate is treated with nitric acid, it is possible to distinguish whether the salt is a sulphate or a carbonate (as in the test for a chloride).

${\mathrm{BaSO}}_{4}+{\mathrm{HNO}}_{3}\to$ (no reaction; precipitate is unchanged)

${\mathrm{BaCO}}_{3}+2{\mathrm{HNO}}_{3}\to \mathrm{Ba}{\left({\mathrm{NO}}_{3}\right)}_{2}+{\mathrm{H}}_{2}\mathrm{O}+{\mathrm{CO}}_{2}$ (precipitate disappears)

## Test for a carbonate

If a sample of the dry salt is treated with a small amount of acid, the production of carbon dioxide is a positive test for a carbonate.

$\mathrm{Acid}+{\mathrm{CO}}_{3}^{2-}\to {\mathrm{CO}}_{2}$

If the gas is passed through limewater and the solution becomes milky, the gas is carbon dioxide.

${\mathrm{Ca\left(OH\right)}}_{2}+{\mathrm{CO}}_{2}\to {\mathrm{CaCO}}_{3}+\mathrm{H}{}_{2}\mathrm{O}$ (It is the insoluble ${\mathrm{CaCO}}_{3}$ precipitate that makes the limewater go milky)

## Test for bromides and iodides

As was the case with the chlorides, the bromides and iodides also form precipitates when they are reacted with silver nitrate. Silver chloride is a white precipitate, but the silver bromide and silver iodide precipitates are both pale yellow. To determine whether the precipitate is a bromide or an iodide, we use chlorine water and carbon tetrachloride ( ${\mathrm{CCl}}_{4}$ ).

Chlorine water frees bromine gas from the bromide and colours the carbon tetrachloride a reddish brown.

Chlorine water frees iodine gas from an iodide and colours the carbon tetrachloride purple.

## Precipitation reactions and ions in solution

1. Silver nitrate ( ${\mathrm{AgNO}}_{3}$ ) reacts with potassium chloride ( $\mathrm{KCl}$ ) and a white precipitate is formed.
1. Write a balanced equation for the reaction that takes place.
2. What is the name of the insoluble salt that forms?
3. Which of the salts in this reaction are soluble?
2. Barium chloride reacts with sulphuric acid to produce barium sulphate and hydrochloric acid.
1. Write a balanced equation for the reaction that takes place.
2. Does a precipitate form during the reaction?
3. Describe a test that could be used to test for the presence of barium sulphate in the products.
3. A test tube contains a clear, colourless salt solution. A few drops of silver nitrate solution are added to the solution and a pale yellow precipitate forms. Which one of the following salts was dissolved in the original solution?
1. $\mathrm{NaI}$
2. $\mathrm{KCl}$
3. ${\mathrm{K}}_{2}{\mathrm{CO}}_{3}$
4. ${\mathrm{Na}}_{2}{\mathrm{SO}}_{4}$
(IEB Paper 2, 2005)

#### Questions & Answers

where we get a research paper on Nano chemistry....?
what are the products of Nano chemistry?
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
revolt
da
Application of nanotechnology in medicine
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
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
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Alexandre
what is the stm
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Rafiq
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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
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
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
What makes metals better to use as wires than non-metals? (please link to bonding type)??? HELP