Chapter 1 Practice Paper: Experimental Chemistry — question paper (print)

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QQ/S3CH/CH1

Secondary 3 · Chemistry (G2 / G3)

Chapter 1 Practice Paper

Experimental Chemistry

Duration: 40 minutes

Total: 30 marks

Name:

Class:

Date:

READ THESE INSTRUCTIONS FIRST

Write your name, class and register number in the spaces at the top of this page.
Answer all questions.
Give numerical answers correct to 3 significant figures unless stated otherwise, with units where a quantity is calculated.
Chemical equations should be balanced, with state symbols shown where the question asks for them.
The number of marks is given in brackets [ ] at the end of each question or part question.
The total number of marks for this paper is shown on its cover.

Original practice material written for the MOE Chemistry syllabus. It is not an official MOE or school examination paper. Chapter 1 (experimental design, separation and purification, chromatography, purity, gas collection).

For Examiner’s Use
Section A	/ 10
Section B	/ 20
Total	/ 30

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

1
Which piece of apparatus delivers exactly 25.0 cm³ of a solution with the greatest precision?
1. Aa 100 cm³ measuring cylinder
2. Ba 25 cm³ pipette
3. Ca 100 cm³ beaker
4. Da 250 cm³ conical flask
( )
2
A beaker holds a cloudy mixture of chalk powder (insoluble) in water. The powder is separated by
1. Aevaporation to dryness
2. Bsimple distillation
3. Cpaper chromatography
4. Dfiltration
( )
3
A pure liquid is boiled gently in a simple distillation. While it distils steadily, the thermometer reading
1. Astays at the liquid’s boiling point
2. Bfalls steadily
3. Crises above the boiling point
4. Dfluctuates randomly
( )
4
Impurities mixed into a solid change its melting behaviour. Compared with the pure solid, the mixture
1. Amelts sharply at a higher temperature
2. Bdoes not melt at any temperature
3. Cmelts over a range starting below the pure melting point
4. Dmelts sharply at exactly the same temperature
( )
5
A gas is less dense than air and insoluble in water. Which collection arrangement is suitable?
1. Acollection over water only
2. Bdownward delivery of air
3. Cupward delivery of air only
4. Dthe gas cannot be collected
( )

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
A student separates a cold, saturated solution of a soluble, heat-stable salt.
1. (a)
  Describe how crystals of the salt are obtained from the solution, naming the point at which heating stops.
  [3]
2. (b)
  State why evaporating the solution to complete dryness gives a poorer product.
  [1]
2
A chromatogram is run on a food dye. The dye spot moves 5.4 cm and the solvent front moves 9.0 cm from the pencil start line.
1. (a)
  Work out the Rf value for this dye spot.
  Rf =[2]
2. (b)
  State one observation that would show the dye is a mixture rather than a pure substance.
  [1]
3. (c)
  Explain why the start line is drawn with pencil rather than ink.
  [2]
3
Pure water is separated from a solution of sodium chloride by simple distillation.
1. (a)
  Explain why the water vapour leaving the flask contains no sodium chloride.
  [2]
2. (b)
  State the position of the thermometer bulb and explain why it matters.
  [2]
3. (c)
  State one reason for adding anti-bumping granules to the flask.
  [1]
4
A factory must check that a liquid sold as ethanol is pure. Pure ethanol boils at 78 °C.
1. (a)
  Describe an experiment to determine the boiling point of the liquid.
  [4]
2. (b)
  The liquid distils with the thermometer climbing slowly from 72 °C to 80 °C throughout. State and justify a conclusion about the sample.
  [2]

— End of paper —