Identifying cations

Question 1

Testing for group 2 mal cations method one

Answer 1

Test 1 – dilute sodium hydroxide
a) Place about 10 drops of 0.1 mol dm–3 barium chloride in a clean test tube. 
Add about 10 drops of 0.6 mol dm–3 sodium hydroxide solution, mixing well.
b) Now continue to add this sodium hydroxide solution, dropwise with gentle shaking, until in excess.
The test tube should not be more than half full. Once completed, dispose of the contents by placing the test tube in a bowl of water.
c) Repeat this test with the calcium bromide, magnesium chloride and strontium chloride

 0.1 mol dm–3 barium chloride solution  0.6 mol dm–3 sodium hydroxide solution  0.1 mol dm–3 calcium bromide solution (or calcium nitrate/potassium bromide)  0.1 mol dm–3 magnesium chloride solution  0.1 mol dm–3 strontium chloride solution.

Question 2

Testing for group 2 mal cations method two

Answer 2

Test 2 – dilute sulfuric acid

a) Place about 10 drops of 0.1 mol dm–3 barium chloride in a clean test tube. 
Add about 10 drops of 1.0 mol dm–3 sulfuric acid, mixing well. 

b) Now continue to add this dilute sulfuric acid, dropwise with gentle shaking, until in excess.
The test tube should not be more than half full. Once completed, dispose of the contents by placing the test tube in a bowl of water.
c) Repeat this test with the calcium bromide, magnesium chloride and strontium chloride

 0.1 mol dm–3 barium chloride solution  1.0 mol dm–3 sulfuric acid  0.1 mol dm–3 calcium bromide solution (or calcium nitrate/potassium bromide)  0.1 mol dm–3 magnesium chloride solution  0.1 mol dm–3 strontium chloride solution.

Question 3

Testing for ammonium ions method and equiment

Answer 3

Test 3: Testing for ammonium ions

a) Place about 10 drops of 0.1 mol dm–3 ammonium chloride in a clean test tube. Add about 10 drops of 0.4 mol dm–3 sodium hydroxide solution. Shake the mixture.
b) Warm the mixture in the test tube gently using a water bath. c) Test the fumes released from the mixture by using forceps to hold a piece of damp red litmus paper in the mouth of the test tube.
d) Dispose of the contents by using the previous method.

 0.1 mol dm–3 ammonium chloride  0.4 mol dm–3 sodium hydroxide solution  red litmus paper  kettle  water bath.

Question 4

equipment

Answer 4

 test tubes and stoppers  test-tube racks  plastic graduated dropping pipettes  deionised or distilled water  forceps