Topic 12 Practice Paper: Experimental techniques and chemical analysis — question paper

Section A: Multiple-choice questions[10 marks]

Choose one answer for each question. Each question is worth 1 mark.

1. 1

   Which apparatus allows an acid to be added to a reaction flask drop by drop while recording the volume added?

   1. AA burette
   2. BA measuring cylinder
   3. CA pipette
   4. DA gas syringe
   ( )
2. 2

   Chalk powder is stirred into water and the mixture is filtered. The material caught on the filter paper is the

   1. Afiltrate
   2. Bsolvent
   3. Csolution
   4. Dresidue
   ( )
3. 3

   Which observation is the positive result of the test for carbon dioxide?

   1. AA glowing splint relights
   2. BLimewater turns milky
   3. CDamp litmus paper is bleached white
   4. DA lighted splint gives a squeaky pop
   ( )
4. 4

   A gas is collected and tested. A glowing splint inserted into the gas relights. The gas is

   1. Ahydrogen
   2. Bchlorine
   3. Coxygen
   4. Dammonia
   ( )
5. 5

   Which technique separates a pure solvent from a solution?

   1. ASimple distillation
   2. BFiltration
   3. CCrystallisation
   4. DPaper chromatography
   ( )
6. 6

   Ethanol (boiling point 78 °C) and water (boiling point 100 °C) are completely mixed. The best way to separate them is

   1. Afiltration
   2. Busing a separating funnel
   3. Ccrystallisation
   4. Dfractional distillation
   ( )
7. 7

   A solution gives a white precipitate with a few drops of aqueous sodium hydroxide. The precipitate dissolves in excess sodium hydroxide but not in excess aqueous ammonia. The cation is

   1. AZn²⁺
   2. BAl³⁺
   3. CCa²⁺
   4. DCu²⁺
   ( )
8. 8

   Which reagents are used in the test for iodide ions in solution?

   1. AAqueous barium nitrate after dilute nitric acid
   2. BAqueous sodium hydroxide and aluminium foil
   3. CAqueous silver nitrate after dilute nitric acid
   4. DAcidified aqueous potassium manganate(VII)
   ( )
9. 9

   In a chromatography experiment a dye moves 3.0 cm while the solvent front moves 12.0 cm. The Rf value of the dye is

   1. A4.0
   2. B0.25
   3. C0.33
   4. D0.75
   ( )
10. 10

    Aqueous sodium hydroxide is added until in excess to a solution containing Cr³⁺ ions. What is observed?

    1. AA light blue precipitate that dissolves
    2. BA red-brown precipitate that does not dissolve
    3. CA colourless solution only
    4. DA grey-green precipitate that dissolves in excess to a green solution
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

1. 11

   A student finds the exact volume of dilute sulfuric acid that neutralises 25.0 cm³ of aqueous potassium hydroxide.

   1. (a)

      Describe how the alkali is measured and transferred to the conical flask.

      [2]
   2. (b)

      Name the apparatus used to add the acid, and state the reading taken at the end point.

      [2]
   3. (c)

      Explain why universal indicator is a poor choice for this experiment.

      [1]
2. 12

   A food scientist analyses two colourless amino acid samples, P and Q, by paper chromatography. After running, the paper is sprayed with ninhydrin and heated. P gives one spot; Q gives two spots.

   1. (a)

      Explain why ninhydrin is needed in this experiment.

      [1]
   2. (b)

      State what the two spots of sample Q show about its composition.

      [1]
   3. (c)

      Spot P moved 5.4 cm while the solvent front moved 9.0 cm. Calculate the Rf value of P.

      [1]
   4. (d)

      Explain why the baseline must be drawn in pencil.

      [1]
   5. (e)

      State one way to confirm that P and a known amino acid are the same substance.

      [1]
3. 13

   After a reaction, a beaker contains a hot mixture of a solid product, dissolved salt and water.

   1. (a)

      Name the technique that removes the solid product from the mixture.

      [1]
   2. (b)

      Name the solid collected and the liquid that passes through.

      [2]
   3. (c)

      Describe how pure salt crystals are then obtained from the filtrate.

      [2]
4. 14

   A colourless liquid, T, may be pure ethanol or a mixture of ethanol and water. Its boiling behaviour is investigated, and a small sample of the liquid is evaporated on a watch glass and tested with anhydrous cobalt(II) chloride paper.

   1. (a)

      The cobalt(II) chloride paper turns pink. State what this shows about liquid T.

      [1]
   2. (b)

      Liquid T boils gradually between 78 °C and 96 °C. State what this shows about T and explain your reasoning.

      [2]
   3. (c)

      Name the technique that would separate T into ethanol and water, and state the property the separation relies on.

      [2]