2019 WAEC (WASSCE) Chemistry Past Questions & Answers

Question 1

Kipps  apparatus can be used to prepare?

Accepted Answer

D. H$_2$S

Answer

A. H$_2$

Answer

B. NH$_3$

Answer

C. O$_2$

Question 2

What is the characteristic of the gas liberated when dilute hydrochloric acid is added to Iron(ii)sulphide?

Accepted Answer

D. turns  lead(ii)ethanoate paper black

Answer

A. turns lime water milky

Answer

B. decolorizes bromine water

Answer

C. gives a pop sound

Question 3

which of the following solutions containing one mole per dm$^3$ of the compound would have the lowest PH?

Accepted Answer

B. hydrochloric acid

Answer

A. ethanoic acid

Answer

C. sodium chloride

Answer

D. sodium hydrogentrioxocarbonate(iv)

Question 4

which of the following pairs of substances has the highest heat of neutralization?

Accepted Answer

A. strong acid and strong base

Answer

B. weak acid and weak base

Answer

C. strong acid and weak base

Answer

D. weak acid and strong base

Question 5

which of the following organic compounds has the lowest boiling point?

Accepted Answer

D. ( CH$_3$ )$_3$

Answer

A. C$_6$H$_14$

Answer

B. C$_5$H$_12$

Answer

C. C$_4$H$_10$

Question 6

What is the solubility of a salt X at 25ºC if the saturated solution of the salt contains 0.28g in 100cm$^3$ of the solution in mol\dm$^3$?  [ X = 56.0g ]

Accepted Answer

A. 0.05

Answer

B. 0.10

Answer

C. 2.60

Answer

D. 2.80

Question 7

in Boyle's law?

Accepted Answer

D. T is constant, V varies inversely with P

Answer

A. T is constant, P varies directly with V

Answer

B. P is constant, V  varies inversely with T

Answer

C. V is constant, P varies directly with T

Question 8

The group to which elements belong in the periodic table is determined by the number?

Accepted Answer

D. valence electrons

Answer

A. electrons

Answer

B. core electrons

Answer

C. valence shells

Question 9

Vinegar is an aqueous solution of?

Accepted Answer

C. ethanoic acid

Answer

A. Hydrochloric acid

Answer

B. ethanedioc acid

Answer

D. hydrofluoric acid

Question 10

If the value of ΔH is positive for a reaction, it means that the reaction is?

Accepted Answer

B. endothermic

Answer

A. exothermic

Answer

C. spontaneous

Answer

D. slow

Question 11

What is the percentage by mass of H in  CH$_3$COOH ?

Accepted Answer

C. 6.7%

Answer

A. 1.7%

Answer

B. 5.0%

Answer

D. 7.1%

Question 12

Which of the substances is non-polar?

Accepted Answer

A. Bromine

Answer

B. Ammonia

Answer

C. Water

Answer

D. Hydrogen Bromide

Question 13

Which of the following pairs of components have the same molecular mass? [ H = 1.0, C = 12.0, O = 16.0 ]

Accepted Answer

C. Carbon (ii) Oxide and Ethene

Answer

A. Ethene and Ethyne

Answer

B. Ethane and Ethene

Answer

D. Carbon (iv) Oxide and Ethyne

Question 14

Which of the following methods is NOT used  for the separation of mixtures?

Accepted Answer

D. Electrolysis

Answer

A. Chromatography

Answer

B. Crystallization

Answer

C. Distillation

Question 15

Consider the following reaction represented by the following equation: C$_2$H$_2$ $^{H_2}_{→}$ X  $^{H_2}_{→}$ Y.           X and Y respectively are?

Accepted Answer

B. ethene and ethane

Answer

A. ethane and ethene

Answer

C. ethyne and ethene

Answer

D. ethane and ethyne

Question 16

When an equilibrium is established between dissolved and undissolved solutes, the solution is said to be?

Accepted Answer

A. Saturated

Answer

B. Unsaturated

Answer

C. Concentrated

Answer

D. Diluted

Question 17

The most suitable indicator for the reaction between NaOH and HCOOH is?

Accepted Answer

D. phenolphthalein

Answer

A. bromocresol

Answer

B. methyl orange

Answer

C. methyl red

Question 18

The name of the compound CH$_3$C(CH$_3$)$_2$CH$_2$CH$_2$CH$_3$

Accepted Answer

D. 2,2 - dimethyl pentane

Answer

A. 2 - methyl butane

Answer

B. 2,2 - dimethyl butane

Answer

C. 2 - methyl pentane

Question 19

When excess chlorine is mixed with ethane at room temperature, the product formed is?

Accepted Answer

A. 1,2-dichloroethane

Answer

B. 1,2-dichloroethene

Answer

C. 1,1-dichloroethane

Answer

D. 1,1-dichloroethene

Question 20

Calcium and magnesium belong to the group of the periodic table because both?

Accepted Answer

D. have same number of valence electrons

Answer

A. are metals

Answer

B. form cations

Answer

C. form colourless salts

Question 21

In a mixture of gases which do not react chemically together, the pressure of the individual gas is?

Accepted Answer

D. partial pressure

Answer

A. atmospheric pressure

Answer

B. vapor pressure

Answer

C. total pressure

Question 22

Which of the following metals reacts slowly with cold water?

Accepted Answer

C. Calcium

Answer

A. Iron

Answer

B. Silver

Answer

D. Pottassium

Question 23

The periodic table is an arrangement of elements according to their?

Accepted Answer

B. Atomic number

Answer

A. Oxidation number

Answer

C. Mass number

Answer

D. Number of neutrons

Question 24

The atoms of $^{64}_{29}$Cu and $^{65}_{30}$Zn have the same number of?

Accepted Answer

C. neutrons

Answer

A. nucleon

Answer

B. electrons

Answer

D. protons

Question 25

The bleaching action of chlorine is through the process?

Accepted Answer

D. Oxidation

Answer

A. Hydration

Answer

B. Hydrolysis

Answer

C. Reduction

Question 26

An organic compound contains 72% carbon, 12% hydrogen and 16% oxygen by mass. What is the empirical formula of the compound? [ H = 1.0. C = 12.0, O = 16.0 ]

Accepted Answer

B. C$_6$H$_{12}$O

Answer

A. C$_3$H$_8$O

Answer

C. C$_6$H$_{12}$O$_2$

Answer

D. C$_{12}$H$_{12}$O$_{11}$

Question 27

The oxidation of chromium in Cr$_2$O$_7)$-2$ ?

Accepted Answer

C. +6

Answer

A. +4

Answer

B. +5

Answer

D. +7

Question 28

consider the following reaction equation: 2NH$_3 $ .+ 3Cl$_2$ → N2 + 6HCl.  NH$_3$ is acting as?

Accepted Answer

A. a reducing agent

Answer

B. a dehydrating agent

Answer

C. a drying agent

Answer

D. an oxidizing agent

Question 29

Which of the following substances can be classified as heavy chemicals?

Accepted Answer

B. H$_2$SO$_4$

Answer

A. CaOCl$_2$

Answer

C. AgNO$_3$

Answer

D. CaO

Question 30

The method used to collect gas in the laboratory depends on its? I. boiling point  II. density  III. smell  IV. solubility in water

Accepted Answer

B. ii and iv only

Answer

A. i and ii only

Answer

C. iii and iv

Answer

D. i, ii, iii and iv

Question 31

consider the reaction represented by the following equation: 2SO$_2$ + O$_2$  ⇌ 2SO$_3$  A decrease in the pressure of the reaction would

Accepted Answer

C. shift the equilibrium position to the left

Answer

A. decrease in the concentration of SO$_2$

Answer

B. have no effect on the reaction

Answer

D. shift the equilibrium position to the right

Question 32

When quicklime dissolves in water?

Accepted Answer

B. heat is evolved

Answer

A. heat is absorbed

Answer

C. oxygen is liberated

Answer

D. hydrogen is given off

Question 33

consider the following reaction equation: 2NH $_3$ .+ 3Cl $_2$ → N2 + 6HCl. NH $_3$ is acting as?

A.a reducing agent
B.a dehydrating agent
C.a drying agent
D.an oxidizing agent

Show answer

Answer: A. a reducing agent

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Accepted Answer

C. 1.5

Answer

A. 0.5

Answer

B. 1.0

Answer

D. 3.0

Question 34

which of the following elements has the highest ionization energy?

Accepted Answer

C. Flourine

Answer

A. Calcium

Answer

B. Chlorine

Answer

D. Magnesium

Question 35

Stoichiometry is based on the law?

Accepted Answer

D. conservation of mass

Answer

A. multiple proportion

Answer

B. constant composition

Answer

C. conservation of energy

Question 36

If the oxidation potential of Mg and Al are +2.37 volts and + 1.66 volts respectively, then the Mg would?

Accepted Answer

D. replace Al

Answer

A. not replace Al

Answer

B. be replaced by Al

Answer

C. remain in the solution

Question 37

Which of the following compounds has coordinate bonds in its structure?

Accepted Answer

A. Al$_2$Cl$_6$

Answer

B. MgCl$_2$

Answer

C. AgCl

Answer

D. NaCl

Question 38

A solid with higher melting and boiling points is likely to be?

Accepted Answer

C. An Electrovalent compound

Answer

A. Covalent compound

Answer

B. A Dative compound

Answer

D. A Non-metal

Question 39

If 6.5g of magnesium ribbon reacts completely with Hydrochloric acid, how many grams of hydrogen gas would be liberated? Mg(s) + 2 HCl(aq) --> MgCl 2(aq) + H 2(g) [ H = 1.0, Mg = 24.0 ]

Accepted Answer

A. 0.54g

Answer

B. 0.70g

Answer

C. 1.08g

Answer

D. 1.40g

Question 40

The properties of a good primary standard solution include the following except?

Accepted Answer

B. low molecular mass

Answer

A. High molecular mass

Answer

C. high degree of purity

Answer

D. readily available

Question 41

Which of the following apparatus is NOT used in volumetric analysis?

Accepted Answer

C. Desiccator

Answer

A. Pipette

Answer

B. Burette

Answer

D. conical flask

Question 42

One of the deductions from Rutherford's alpha particle scattering experiment is that?

Accepted Answer

C. nuclei of atoms are positively charged

Answer

A. electrons are negatively charged

Answer

B. electrons have a negligible mass

Answer

D. protons are positively charged

Question 43

How many moles of carbon(iv)oxide contains 16.0g of oxygen? [ C = 12.0, O = 16.0 ]

Accepted Answer

D. 0.50 mol

Answer

A. 0.20 mol

Answer

B. 0.25 mol

Answer

C. 0.40 mol

Question 44

The process by which alkanoic acid reacts reversibly with alkanols is known as?

Accepted Answer

B. esterification

Answer

A. saponification

Answer

C. carboxylation

Answer

D. halogenation

Question 45

If a catalyst is added to a system, the temperature and the pressure remain constant, there would be no effect on the?

Accepted Answer

D. heat of reaction

Answer

A. activation energy of the reaction

Answer

B. rate of the reaction

Answer

C. rate of the reverse reaction

Question 46

A sample of air was bubbled into water. The PH of the water slowly changed from 7 to 6. Which of the following gases in the samples caused the change?

Accepted Answer

A. carbon(iv)oxide

Answer

B. carbon(ii)oxide

Answer

C. nitrogen

Answer

D. oxygen

Question 47

which of the following reagents could be used to distinguish between propan-1-ol and propan-2-ol

Accepted Answer

B. I$_2$ / OH-

Answer

A. H+ / K2Cr2O7

Answer

C. CH$_3$COOH

Answer

D. NaCl

Question 48

Biotechnology is applied in the?

Accepted Answer

A. treatment of sewage

Answer

B. treatment of water

Answer

C. purification of chemicals

Answer

D. purification of metals

Question 49

Which of the following compounds is formed by the oxidation of ethanol?

Accepted Answer

D. CH$_3$CO$_2$H

Answer

A. C$_2$H$_4$CO$_2$H

Answer

B. C$_2$H$_5$CO$_2$H

Answer

C. CH$_3$OH

Question 50

The number of electrons in the 3d orbital of  $_24$Cr is

Accepted Answer

D. 5

Answer

A. 2

Answer

B. 3

Answer

C. 4

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