Test for ions and gases

Question 1

Describe tests for Li+, Na+, K+, Ca2+

Answer 1

Platinium or nichrome wire cleaned by dipping it into concentrated hydrochloric acid and holding it in a hot bunsen flame until the wire doesn't give any colour to the flame. Wire is dipped back into acid. into sample of the solid and back into flame.
Lithium - red
Sodium - orange
Potassium - Lilac
Calcium - Brick-red

Question 2

Describe tests for NH4+

Answer 2

Sodium hydroxide reacts with ammonium salts to produce ammonia gas. Ammonia turns damp red litmus paper blue. There is no precipitate but there is a smell.
NH4Cl + NaOH —–> NaCL + NH3 + H2O

Question 3

Describe tests for Cu2+, Fe2+ and Fe3+

Answer 3

Copper: blue precipitate formed
CUSO4 + 2NaOH -----> Cu(OH)2 + NA2SO4
Iron (II): green precipitate formed
FeSO4 + 2NaOH -----> Fe(OH)2 + Na2SO4
Iron (III): orange-brown precipitate formed
FECl3 + 3NaOH -----> Fe(OH)3 + 3NaCl

Question 4

Describe tests for Cl, Br and I

Answer 4

Make a solution of suspected chloride, bromide or iodide ion. Add enough dilute nitric acid to make it acidic and add silver nitrate solution.
Chlorine: white - Cl- + HNO3 + AgNO3 —–> AgCL
Bromine: cream - BR- + HNO3 + AGNO3 —–> AgBr
Iodine: yellow - I- + HNO3 + AgNO3 —–> AgI

Question 5

Describe tests for SO4

Answer 5

Make a solution of your suspected sulfate in pure water. Add enough dilute hydrochloric acid to make it acidic and add barium chloride solution. A sulfate will produce a white precipitate of barium sulfate. It is acidified to destroy other compounds which might also produce a white precipitate.
BA2+ _ SO4 —–> BaSO4

Question 6

Describe tests for CO3

Answer 6

Add dilute nitric acid to a solid carbonate, carbon dioxide will be produced. Nitric acid will produce a solute salt.
CO3 + 2H+ —–> CO2 + H2O

Question 7

Describe the test for hydrogen

Answer 7

Hydrogen is less dense than air and insoluble in water so it is collected over water or upwards into a test tube. Hydrogen pops when a lighted split is held over the mouth of the tube.

Question 8

Describe the test for oxygen

Answer 8

Same density as air and is collected downwards into a test tube. Soluble in water so can be collected over water. Relights a glowing splint.

Question 9

describe the test for carbon dioxide

Answer 9

Denser than Ari and collected downwards into a test tube. Soluble in water so collected over water as well. Turns limewater cloudy.

Question 10

Describe the test for chlorine

Answer 10

Denser than Ari, collects downwards into test tube. Too soluble to collect over water so it is done over concentrated salt solution. Bleaches damp litmus paper.

Question 11

Describe the test for ammonia

Answer 11

Less dense than air and extremely soluble in water, collected upwards into a test tube. Turns damp red litmus paper blue.