Chapter 6 Practice Paper: Qualitative Analysis — question paper

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

1. 1

   Aqueous sodium hydroxide is added dropwise to a solution of iron(II) sulfate. The precipitate formed is

   1. Alight blue
   2. Bgreen
   3. Cred-brown
   4. Dwhite
   ( )
2. 2

   Which cation forms a white precipitate with aqueous ammonia that dissolves in excess to give a colourless solution?

   1. ACa²⁺
   2. BAl³⁺
   3. CZn²⁺
   4. DNH₄⁺
   ( )
3. 3

   To test for sulfate ions, the solution is first acidified and then

   1. Asilver nitrate solution is added
   2. Bbarium chloride solution is added
   3. Caluminium foil is added and the mixture warmed
   4. Dlimewater is bubbled through
   ( )
4. 4

   An unknown gas is bubbled through acidified potassium manganate(VII) and the purple colour disappears. Which gas could it be?

   1. Ahydrogen
   2. Boxygen
   3. Ccarbon dioxide
   4. Dsulfur dioxide
   ( )
5. 5

   Dilute hydrochloric acid is added to a solid. Bubbling is seen and the gas turns limewater milky. Which ions does the solid contain?

   1. Achloride ions
   2. Bnitrate ions
   3. Csulfate ions
   4. Dcarbonate ions
   ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided. Show all necessary working. Give numerical answers to 3 significant figures where appropriate, with units.

1. 1

   A colourless solution contains one cation. Aqueous sodium hydroxide is added dropwise and then in excess, and the experiment is repeated with aqueous ammonia.

   Observations for the unknown solution

   Reagent	Few drops	In excess
   aqueous sodium hydroxide	white precipitate	precipitate dissolves
   aqueous ammonia	white precipitate	precipitate remains

   1. (a)

      Use the table to identify the cation. Explain how the observations lead to your answer.

      [3]
   2. (b)

      Write the ionic equation for the formation of the white precipitate with aqueous sodium hydroxide.

      [2]
   3. (c)

      State one observation that would change your answer to zinc.

      [1]
2. 2

   A student investigates a white solid, W. Test 1: dilute hydrochloric acid is added — W fizzes and a gas turns limewater milky.

   1. (a)

      Identify the anion in W and name the gas responsible for the limewater result.

      [2]
   2. (b)

      Write the ionic equation for the reaction producing the gas.

      [2]
   3. (c)

      Describe how the student could find out which cation W contains, assuming a solution of W is colourless and gives no precipitate with aqueous ammonia.

      [1]
3. 3

   Ammonium sulfate is a common fertiliser. A chemist confirms its two ions with separate tests on samples of a solution of the salt.

   1. (a)

      Describe the test for the ammonium ion and give the positive result.

      [2]
   2. (b)

      Describe the test for the sulfate ion and give the positive result.

      [2]
   3. (c)

      Explain why warming is needed in the ammonium test.

      [1]
   4. (d)

      Write the ionic equation for the ammonia-forming reaction.

      [1]
4. 4

   Six unlabelled gas cylinders are known to contain ammonia, carbon dioxide, chlorine, hydrogen, oxygen and sulfur dioxide.

   1. (a)

      State one test, with its positive result, that tells hydrogen from oxygen.

      [1]
   2. (b)

      State one test, with its positive result, that tells ammonia from chlorine.

      [1]
   3. (c)

      State one test, with its positive result, that tells carbon dioxide from sulfur dioxide.

      [1]