Required practical 4

Question 1

Testing for Group 2

Answer 1

1. Add dilute NaOH drop wise to test tube containing solution
   - Observe the precipitate formed
2. Continue adding dilute NaOH until it is in excess
   - Observe the precipitate formed

Question 2

Group 2 - results

Answer 2

Mg - Slight white –> White
Ca - slight white –> slight white
Sr - slight white –> slight white
Ba - no change –> no change

Question 3

Testing for Ammonium ions

Answer 3

1. Add dilute NaOH to solution
2. Heat gently
3. Hold damp red litmus paper above test tube

Question 4

Ammonium ions - results

Answer 4

If Ammonia gas is given off then ammonium ions are present - this is shown by red litmus paper turns blue

Question 5

Why must litmus paper be damp when testing for ammonium ions

Answer 5

To allow the ammonia gas to dissolve

Question 6

Ammonium ions - equation

Answer 6

NH4+ + OH- –> NH3 + H2O

Question 7

Testing for sulfate ions

Answer 7

1. Add dilute HCL
2. Add Barium chloride

Question 8

Sulfate ions - result

Answer 8

White precipitate of BaSO4 is produced

Question 9

Sulfate ions - equation

Answer 9

Ba2+ + SO42- –> BaSO4

Question 10

Testing for hydroxide ions

Answer 10

1. Add universal indicator
   Or
2. Dip red litmus paper into solution

Question 11

Hydroxide ions result

Answer 11

1. Universal indicator turns blue
2. Red litmus paper turns blue

Question 12

Testing for Halide ions

Answer 12

1. Add dilute nitric acid
2. Add silver nitrate

Question 13

Halide ions - results

Answer 13

Chloride - white precipitate that dissolves with dilute ammonia Bromide - cream precipitate that dissolves with concentrated ammonia
Iodide - yellow precipitate

Question 14

What is the purpose of dilute nitric acid when testing for halide ions

Answer 14

Removes any carbonate ions which may form silver carbonate - precipitate

Question 15

Testing for carbonate ions

Answer 15

1. Add dilute acid
2. Bubble gas produced through limewater

Question 16

Carbonate ions - results

Answer 16

1. Effervescence
2. Carbon dioxide turns limewater cloudy

Question 17

Carbonate ions - equation

Answer 17

CO32- + 2H+ –> CO2 + H2O