Chemistry 5070 · O Level · Identification of ions and gases

Identification of ions and gases — practice question

A student carries out a set of tests with aqueous solution P and aqueous solution Q.
(a(i))[2]

The tests carried out on P are listed in Table 3.1. Test 1: flame test, observation: orange-red flame. Test 2: add aqueous ammonia. Describe how the student carries out a flame test.

(a(ii))[1]

Describe one observation expected in test 2 using the observation in test 1 as a guide.

(a(iii))[3]

Describe one further test to confirm the identity of the cation in P. Include the result of a positive test.

(a(iv))[1]

Identify the cation in P.

(b(i))[1]

Solution Q is acidic. The tests carried out on Q are listed in Table 3.2. Test 3: add five drops of universal indicator, observation: colour change. Test 4: add a piece of magnesium ribbon, observation: magnesium ribbon disappears. Test 5: add dilute nitric acid followed by aqueous barium nitrate, observation: white precipitate. Describe the expected colour change in test 3.

(b(ii))[1]

A gas is produced in test 4. Predict one other observation the student would make in test 4.

(b(iii))[1]

Predict the identity of the gas produced in test 4.

(b(iv))[2]

Describe a test to confirm the identity of this gas. Include the result of a positive test.

(b(v))[2]

Q contains one cation and one anion. Identify the cation and the anion in Q.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: M1: place a wire / splint into P / put P into spray bottle

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