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Cambridge International Examinations Cambridge International General Certificate of Secondary Education

CHEMISTRY Paper 3 Theory (Core)

Candidates answer on the Question Paper. No Additional Materials are required.

0620/31 October/November 2018

1 hour 15 minutes

READ THESE INSTRUCTIONS FIRST

Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES.

Answer all questions. Electronic calculators may be used. A copy of the Periodic Table is printed on page 16. You may lose marks if you do not show your working or if you do not use appropriate units.

At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question.

The syllabus is approved for use in England, Wales and Northern Ireland as a Cambridge International Level 1/Level 2 Certificate.

This document consists of 16 printed pages.

IB18 11_0620_31/3RP ? UCLES 2018

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1 (a) The electronic structures of five atoms, A, B, C, D and E, are shown.

A

B

C

D

E

Answer the following questions about these structures. Each structure may be used once, more than once or not at all. State which structure, A, B, C, D or E, represents:

(i) an atom of a metallic element ....................................................................................... [1]

(ii) an atom with a proton number of 13 ............................................................................. [1]

(iii) an atom of phosphorus ................................................................................................. [1]

(iv) an atom with only two shells of electrons ..................................................................... [1]

(v) an atom which forms a stable ion with a single negative charge. ................................. [1]

(b) Complete the table to show the number of electrons, neutrons and protons in the carbon atom and potassium ion shown.

number of electrons

number of neutrons

number of protons

164C

6

1490K+

21

[3]

[Total: 8]

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3 2 (a) The table shows the ions present in a 1000cm3 sample of blood plasma.

ion present

sodium potassium

calcium magnesium

chloride hydrogencarbonate

phosphate sulfate

formula of ion

Na+ K+ Ca2+ Mg2+ Cl? HCO3? PO43? SO42?

mass present in the 1000cm3 sample/g

3.25 0.16 0.10 0.04 3.65 1.50 0.64 0.10

Answer these questions using only information from the table.

(i) Which positive ion is present in the lowest concentration?

....................................................................................................................................... [1]

(ii) Give the name of the compound formed from K+ and Cl? ions.

....................................................................................................................................... [1]

(iii) Calculate the mass of potassium ions present in 200cm3 of this blood plasma.

mass of potassium ions = .............................. g [1]

(iv) When the 1000cm3 sample of blood plasma is crystallised, several compounds are formed.

Suggest the name of the compound which forms the greatest mass of crystals.

....................................................................................................................................... [1]

(b) Describe a test for potassium ions.

test .............................................................................................................................................

result .......................................................................................................................................... [2]

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(c) Blood plasma also contains proteins. Proteins are present in food.

Which one of the following substances is also present in food? Draw a circle around the correct answer.

carbohydrate hematite poly(ethene) terylene [1]

(d) Compound S is one of the monomer units used to make proteins. Its structure is shown. compound S

H2N CH COOH CH2 OH

(i) On the structure, draw a circle around the alcohol functional group.

[1]

(ii) Deduce the molecular formula of compound S showing the number of carbon, hydrogen, oxygen and nitrogen atoms.

....................................................................................................................................... [1]

[Total: 9]

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5 3 (a) The apparatus used for distillation is shown.

thermometer

flask

..........................................

aqueous copper(II) sulfate

(i) Complete the box to name the apparatus.

[1]

(ii) Describe and explain how the water is separated from the aqueous copper(II) sulfate by distillation.

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [3]

(b) A sample of solid hydrated copper(II) sulfate is heated gently in a test-tube.

CuSO4.5H2O

hydrated copper(II) sulfate

CuSO4 + 5H2O

Solid hydrated copper(II) sulfate is blue.

Describe two observations when the sample of solid hydrated copper(II) sulfate is heated gently in a test-tube.

1 .................................................................................................................................................

2 ................................................................................................................................................. [2]

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6 (c) Copper(II) sulfate can be prepared by heating an excess of copper(II) oxide with dilute

sulfuric acid. (i) Complete the chemical equation for this reaction.

CuO + H2SO4 CuSO4 + ..................... [1]

(ii) What method is used to separate the excess copper(II) oxide from the solution? ....................................................................................................................................... [1]

(d) Copper(II) oxide can be reduced by hydrogen. CuO + H2 Cu + H2O

How does this equation show that copper(II) oxide is reduced? .................................................................................................................................................... .............................................................................................................................................. [1]

(e) The chemical equation for the reaction of copper with concentrated nitric acid is shown. Cu + 4HNO3 Cu(NO3)2 + 2NO2 + 2H2O

Complete the word equation for this reaction.

copper +

nitric acid

........................... + ........................... + ...........................

...........................

...........................

[2]

[Total: 11]

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7

4 (a) The structure of citraconic acid is shown.

H3C

COOH

C

C

H

COOH

Citraconic acid is an unsaturated compound. (i) What feature of the structure of citraconic acid shows that it is unsaturated?

....................................................................................................................................... [1] (ii) Describe a test for an unsaturated compound.

test ...................................................................................................................................... result ................................................................................................................................... [2]

(b) Ethanoic acid has a carboxylic acid functional group.

Draw the structure of the carboxylic acid functional group. Show all of the atoms and all of the bonds.

[1]

(c) Complete the definition of a homologous series using words from the list.

chemical compounds elements functional hydrocarbons physical

A homologous series is a family of similar .............................. with similar ..............................

properties due to the presence of the same .............................. group.

[3]

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(d) The graph shows how the pH of a dilute acid in a conical flask changes as aqueous sodium hydroxide is added to it.

14

12

10

8

pH 6

4

2

0 0 5 10 15 20 25 30 35

volume of aqueous sodium hydroxide added / cm3

(i) Describe how the pH changes as the aqueous sodium hydroxide is added.

.............................................................................................................................................

.............................................................................................................................................

....................................................................................................................................... [2]

(ii) What is the pH of the dilute acid before the aqueous sodium hydroxide is added?

....................................................................................................................................... [1]

(iii) What volume of aqueous sodium hydroxide has been added when the pH reaches pH7?

....................................................................................................................................... [1]

[Total: 11]

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