RP4

Question 1

How do you test for group 2 metal cations?

Answer 1

● Place 10 drops of a group 2 compound in test tube (0.1 mol dm-3).
● Add 10 drops of 0.6 mol dm-3 NaOH to test tube. Record any observations.
● Continue to add NaOH so it is in excess. Record any observations.
● Repeat with other group 2 compounds.

Question 2

What are the results from these reactions? (How do you test for group 2 metal cations?)

Answer 2

check

Question 3

How would you distinguish between calcium bromide and strontium chloride?

Answer 3

● Place 10 drops of BaCl2 (0.1 mol dm-3) in a test tube.
● Add 10 drops of sulfuric acid (1 mol dm-3). Record
observations.
● Continue to add H2SO4 until in excess. Record
observations.
● Repeat for other the group 2 compounds

Question 4

How do you test for ammonium (NH +)
ions?

Answer 4

● Place 10 drops of NH4Cl into a test tube.
● Add 10 drops of NaOH solution. Shake.
● Warm the solution in the test tube.
● Test the gas released with damp red litmus
paper.
● If it goes blue, ammonium ions are present.

Question 5

What are the overall results for the Group 2 reactions?

Answer 5

check

Question 5

What are the results from these reactions? (How would you distinguish between calcium bromide and strontium chloride?)

Answer 5

check

Question 6

How do you test for group 7/halide ions?

Answer 6

● To the compound being tested, add nitric acid and silver nitrate. Record observations.
● To samples of this solution, add dilute and then concentrated ammonia.

Question 7

What are the results from these reactions? (How do you test for group 7/halide ions?)

Answer 7

check

Question 8

How do you test for hydroxide (OH-) ions?

Answer 8

1. Test a 1 cm depth of solution in a test tube with red litmus paper or universal indicator paper.
2. Record your observations.
3. Sodium hydroxide will turn damp red litmus paper
   blue.

Question 9

How do you test for carbonate (CO 2-)
ions?

Answer 9

● Put 2 cm3 of Ca(OH)2 into a test tube.
● Add 3 cm3 Na2CO3 (0.5 mol dm–3) in another test tube
then add an equal volume of dilute HCl (1.0 mol dm–3).
● Immediately put in delivery tube with open end into the
Ca(OH)2 test tube.
● If Ca(OH)2 goes cloudy, carbonate ions were present in
the other test tube.

Question 10

How do you test for sulfate (SO 2-) ions?

Answer 10

● Add HCl and BaCl2 to the suspected sulfate solution.
● If sulfate ions are present, a white precipitate of BaSO4 will form.

Question 11

What is the order of testing ions? (Carbonate, halide and sulfate)

Answer 11

Carbonate → Sulfate → Halide

This prevents false positive results occurring i.e. Unexpected insoluble precipitates such as Ag2SO4, Ag2CO3 and BaCO3 could form.