ZIMSEC O Level Chemistry Paper 1 November 2019

Question 1

Diffusion

Which gas has the smallest rate of diffusion?

Amethane
Bammonia
Ccarbon dioxide
Dhydrogen chloride

Question 2

Ions

Which diagram correctly represents a sulphide ion, S

^{2-}

Question 3

Experimental techniques

Which apparatus is used to measure an exact volume of 25.00 cm

^3

Aa 50.00 cm $^3$ burette
Ba 25.00 cm $^3$ pipette
Ca 25.00 cm $^3$ conical flask
Da 25.00 cm $^3$ measuring cylinder

Question 4

What is the volume occupied by three moles of carbon dioxide at r.t.p?

A24 dm $^3$
B28 dm $^3$
C72 dm $^3$
D84 dm $^3$

Question 5

Chemical formulae

The chemical formula 2NH

_3

represents

Asix molecules of hydrogen.
Btwo molecules of ammonia.
Ctwo molecules of nitrogen.
Dtwo atoms of ammonia.

Question 6

Energy changes

An exothermic reaction is one which has

Amore gaseous reactants than products.
Bmore gaseous products than reactants.
Ca greater bond formation energy than bond breaking energy.
Da greater bond breaking energy than bond formation energy.

Question 7

Extraction of metals

The main function of limestone in the blast furnace is to

Aoxidise iron ore.
Breduce iron ore.
Cremove impurities.
Dremove excess carbon.

Question 8

Water pollution

Which gas decreases in concentration during eutrophication in a pond?

Ahydrogen
Bmethane
Cnitrogen
Doxygen

Question 9

Waste management

Which method of waste disposal is a source of carcinogens?

Abio-digestion
Bincineration
Crecycling
Dlandfilling

Question 10

Redox

What happens to the oxidation number of nickel when nickel ore, NiS, is changed to pure nickel?

Aincreases to +1
Bdecreases to zero
Cdecreases to +2
Dincreases to zero

Question 11

Pollution

Which chemical is a pollutant from gold processing?

AHg
BAl $_2$ (SO $_4$ ) $_3$
CHCl
DPb

Question 12

Industrial chemistry

The stages show reactions that occur in the contact process.

At which stage is the formation of an acid spray prevented?

AS + O $_2$ $\rightarrow$ SO $_2$
B2SO $_2$ + O $_2$ $\rightleftharpoons$ 2SO $_3$
CSO $_3$ + H $_2$ SO $_4$ $\rightarrow$ H $_2$ S $_2$ O $_7$
DH $_2$ S $_2$ O $_7$ + H $_2$ O $\rightarrow$ 2H $_2$ SO $_4$

Question 13

Metals

Which one is a chemical property of a metal?

Aforms positive ions
Bforms negative ions
Cforms acidic oxides
Dforms coloured solutions

Question 14

Reactivity series

Which element is least reactive?

Question 16

Alloys

Which metal is added to steel to give it anti-corrosion properties?

Achromium
Bcopper
Czinc
Dgold

Question 17

Acids and bases

The pH values of four solutions, W, X, Y and Z, are shown in the table.

Solution W has pH 3, X has pH 5, Y has pH 7 and Z has pH 11.

Which solution can be used to neutralize an acidic soil?

Question 18

Salt preparation

The correct order of preparing some salts from a metal and an acid is

Acrystallisation $\rightarrow$ evaporation $\rightarrow$ displacement $\rightarrow$ filtration.
Bdisplacement $\rightarrow$ filtration $\rightarrow$ evaporation $\rightarrow$ crystallisation.
Cevaporation $\rightarrow$ crystallisation $\rightarrow$ filtration $\rightarrow$ displacement.
Dfiltration $\rightarrow$ evaporation $\rightarrow$ displacement $\rightarrow$ crystallisation.

Question 19

Redox

Which substance is reduced in the reaction shown?

CaO + C $\rightarrow$ Ca + CO $_2$

ACaO
BC
CCa
DCO $_2$

Question 20

Which is not a reason for electroplating metals?

Adecorating
Bprotecting
Cimproving purity
Dimproving electrical conductivity

Question 21

Water

Lathering of soap is a test for the

Apurity of water.
Bacidity of water.
Chardness of water.
Dalkalinity of water.

Question 22

Stoichiometry

Ammonia gas reacts with dilute hydrochloric acid as shown in the equation:

NH $_{3(g)}$ + HCl $_{(aq)}$ $\rightarrow$ NH $_4$ Cl $_{(aq)}$

What mass of ammonium chloride is formed if 8.5 g of ammonia gas is used?

A2.70 g
B4.25 g
C8.50 g
D26.75 g

Question 23

Empirical formula

An organic compound has 92.3 % carbon and 7.7 % hydrogen by mass.

The empirical formula of the compound is

AC $_3$ H $_5$ .
BC $_2$ H $_3$ .
CCH $_2$ .
DCH.

Question 24

Empirical formula

A hydrocarbon has an empirical formula of CH $_2$ and a relative molecular mass of 28.

What is the percentage composition of carbon in the hydrocarbon?

A14 %
B21 %
C50 %
D86 %

Question 25

Redox

A breathalizer is an instrument used to measure the amount of alcohol in a breath. The device contains potassium dichromate which reacts with alcohol in the breath.

If the breath contains alcohol the colour changes from

Agreen to orange.
Borange to green.
Cpink to purple.
Dpurple to pink.

Question 26

Hydrocarbons

Which molecular formula could be that of candle wax?

AC $_4$ H $_{10}$
BC $_6$ H $_{12}$
CC $_8$ H $_{18}$
DC $_{20}$ H $_{42}$

Question 27

Esters

Ethanoic acid reacts with methanol according to the equation

CH $_3$ COOH + CH $_3$ OH $\rightarrow$ CH $_3$ COOCH $_3$ + H $_2$ O

What is the name of the ester formed?

Amethylpropanoate
Bmethylethanoate
Cethylethanoate
Dethylmethanoate

Question 28

Cracking

A hydrocarbon, X, can crack as shown

X $\xrightarrow{\text{heat}}$ C $_2$ H $_4$ + C $_8$ H $_{18}$

What could be X?

AC $_6$ H $_{14}$
BC $_8$ H $_{18}$
CC $_{10}$ H $_{22}$
DC $_{16}$ H $_{36}$

Question 29

Combustion

One of the products of heating methane in excess oxygen is

Acarbon.
Bsoot.
Ccarbon monoxide.
Dcarbon dioxide.

Question 30

Polymers

Amino acids react to form a large protein molecule and water as shown.

amino acids $\rightarrow$ protein molecule + water.

The process is called

Ahydrolysis.
Belimination.
Caddition polymerisation.
Dcondensation polymerisation.

Question 31

Organic chemistry

An organic compound Q reacted with one mole of hydrogen in the presence of a catalyst.

What could be Q?

Aan alcohol
Ba carboxylic acid
Can alkene
Dan alkane

Question 32

Which reaction can be used to distinguish ethane from ethene?

Areacting both with chlorine in UV light
Breacting both with bromine water in UV light
Creacting both with bromine water in the dark
Dreacting both with hydrogen gas

Question 33

Organic reactions

The reaction between an alkene and bromine in the dark is

Aan addition reaction.
Ban oxidation reaction.
Ca reduction reaction.
Da polymerisation reaction.

Question 34

Energy changes

The diagrams show some energy profiles of different reactions.

Which diagram represents the reaction with the largest negative enthalpy change of reaction?

Question 35

Qualitative analysis

A solution of silver nitrate was placed in four different test tubes and subjected to different tests as shown in the diagram.

In which test tube will the red litmus paper change to blue?

Question 36

Polymers

Packaging material made of polyethene cannot be disposed of by land filling because it is

Apoisonous to animals.
Bnon biodegradable.
Ca condensation polymer.
Dan addition polymer.

Question 37

Medicines

Which statement is true about the use of plants in traditional medicine?

Athere are clear prescriptions and dosages
Bthey can improve the health of a person
Cthey are not poisonous
Dthey do not cause any allergies

Question 38

Separation techniques

Purity of a substance can be tested by

Acrystallisation.
Bchromatography.
Cfiltration.
Dprecipitation.

Question 39

Water treatment

In the purification of water the coagulant used is

Aaluminium sulphate.
Bpotassium sulphate.
Ccopper sulphate.
Dbarium sulphate.

Question 40

Minerals

Which statement correctly defines the term *mineral beneficiation*?

Aexporting the ore for quick cash benefits
Busing the ore to benefit the community
Cprocessing ore to add value and fetch higher prices
Dselling precious stones on the black market to benefit from the high prices

Chemistry Paper 1 November 2019

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The questions

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 16

Question 17

Question 18

Question 19

Question 20

Question 21

Question 22

Question 23

Question 24

Question 25

Question 26

Question 27

Question 28

Question 29

Question 30

Question 31

Question 32

Question 33

Question 34

Question 35

Question 36

Question 37

Question 38

Question 39

Question 40

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