WAEC 2023 EXPECTED QUESTION AND ANSWER: Chemistry

Examination malpractices may lead to a repeat of the subject or
suspensions don’t be involved.

TIME ALLOWED: 2HRS. 30MINS

1.If the relative molecular mass of an element is not a whole number, it
can be deduced that the element is
a. naturally radioactive b. abundant in nature c. a transition metal d. an
isotopic mixture
2. Which of the following decreases when a given mass of gas is
compressed to half its initial volume? A. average intermolecular distances
b. frequency of collisions
c. number of molecules present
d. atomic radius of each particle
3. Calculate the mass of chlorine gas which occupies a volume of 1.12dm
at s.t.p.
3
4. Determine the mass of sulphur(iv) oxide obtained when 91.0g of oxygen
reacts completely with sulphur according to the following equations
S +O ——-SO (g).(S=32,O=16)
a.123g b.139g c.155g d.182g
5. Which of the following elements form an ionic chloride? A. magnesium
b .carbon c. phosphorus d. Hydrogen
6. A sample of orange juice is suspected to have been contaminated with
a yellow dye. Which of the following methods can be used to detect the
dye?
Decantation b) chromatography (c) distillation (d) ltration (e) evaporation

 

7. The bond between two iodine molecules is (a).co-ordinate bond (b)
electrovalent bond (c).ionic bond (d)van der waal’s forces
8. Bonds between a highly electronegative atom and a hydrogen from
another molecule is called (a).hydrogen bond (b).covalent bond
(c).intermolecular forces (d).ligand.
9.The nitride ion is N .What is the formula of the nitride of an alkali metal
X.
a.X N B.XN C.X N d.X N
10.What type of chemical bonding is involved in the formation of NH
from a molecule of ammonia and a proton. a. Hydrogen bonding b. coordinate covalent bonding c. electrovalent bonding d. covalent bonding
11. Which of the following properties of elements decreases generally
across a period in the periodic table? (a) electronegativity (b) electron
anity (c) atomic radius (d) ionization energy.
3
-3
3 5 3 2 3 3
4
+
13. One of the following will not aect a chemical system at equilibrium
a. Temperature b. Catalyst c. Pressure d. Concentration
14. The product of an endothermic reaction are
a. higher in enthalpy than the reactant b. lower in enthalpy than the
reactant
c .the same in enthalpy as the reactant d. the change in enthalpy is less
than zero
15. Which of the following metals will react with cold water to produce
hydrogen gas?
a. calcium b. aluminium c. copper d .magnessium.

 

16. Which component of air is removed when air is bubbled through a
solution of alkaline pyrogallol? a.carbon (iv)oxide b.Nitrogen c.Oxygen
d.Helium
17.Oygen is obtained from liquid air by a. Fermentation b. Fractional
distillation
ÄG is zero d. ÄG is constant.
18.Halogens are
a. strong reducing agents
b. strong oxidizing agents
c. strong actions d. strong donors of electrons
19. Chlorine is best collected by a. upward displacement of air b.
downward displacement of air c. over water d .over mercury
20. Which of the oxides of nitrogen is a neutral oxide? a.N O b.NO
C.N O d.NO
21.Plastic sulphur is a. A crystalline allotrope of sulphur b. A super
cooled form of sulphur
c. A form of sulphur rings packed together
d. Forms monoclinic sulphur when left
22.What will happen if more heat is
applied to the following system at equilibrium? X
+3Y ¬?2XY
ÄH=xkjmol
a. the yield of XY will increase b. more of XY will decompose c. more
of X will react
D. the forward reaction will go into completion.
23.Eervescence occurs when water comes in contact with a.calcium b.
2 4 2
2 5
2 2 3(g)
-1
3 3
2
copper c. sulphur d. lead
24. 1. The gas that can be best collected by downward displacement of air
(a) chlorine (b) carbon(iv)oxide (c) sulphur (iv)oxide (d) ammonia.

 

Consider the reaction : CO(g)+H O?¬CO (g)+H (g)
ÄH=-41KJmol
25.Which of the following conditions has no eect on the equilibrium
mixture?
a. pressure applied on the system b. temperature of the system c.
removal of one of the reactants d. removal of the products as they are
formed.
26.If copper has an oxidation state of +2 in a complex ion represented as
(Cu(X) )
What is the electrical charge of X? a.-4 b.-2 c.0 d.-2
27.Which of the following equation represents direct combination?
a. Fe + e —Fe b. H +OH —-H O c. Zn +Cl —–ZnCl (s)
d. Ag +Cl —–AgCl
28. The following are characteristics of colloids except
a. tyndal eect on light beam b. solid phase are removed by dialysis c.
colloidal particles are larger than that of suspensions
d. colloidal particles are separated using parchment membranes.
29. 144 g of KCl dissolved in 1dm of water at 90°C in the presence of
excess crystals of KCl. Calculate the solubility of KCl at this temperature.
(K=39,Cl=35.5)
a.0.89moldm b.1.93moldm c.1.75 moldm d.1.5moldm
30. What is the volume occupied by 2 moles of ammonia at S.T.P?
A. 44.8dm B. 22.4dm C. 11.2dm
D. 5.6dm
2 2 2
-1
4
+2
3+
(aq)
– 2+ +
(aq)
– 2 (aq) 2 2
(aq)
–
(s)
3
-3 -3 -3 -3
-3 -3 -3
-3

 

31.Cr O + 14H + xe
2Cr + 7H O
The number of moles(x) of electrons in the above half cell equation is: (a)
2 (b) 4 (c) 7 (d) 6
32. the volume occupied by 0.4g of hydrogen gas at STP is (H=1.00, molar
volume at STP =22.4 dm )
(a) 2.24 dm (b) 4.48dm (c) 22.4dm (d) 8.96 dm
33. A measure of degree of disorderliness in a chemical system is known
as: (a)enthalpy (b) free energy (c) entropy (d) activation energy
34. H + x
2HX ÄH=positive. In the above reaction,a decrease
in temperature will:
(a) decrease the concentration of HX
(b) favour the forward reaction
(c) favour the yield HX
(d) have no eect on the equilibrium position
35. 3Fe +4H O
Fe
O + 4H .The equilibrium constant K of the
reaction above is represented as: (a) [H ] /[H O] (b) [Fe]
[H O] /[Fe O ] [H ] (c)[Fe O ][H ] /[Fe] [H O]
(d)[H ] /[H ]
36. What is the quantity of electricity produced when a current of 0.5 A is
passed for 5 hours 45 minutes (F=96500)? (a)0.11F (b)0.22F (c) 0.12F (d)
1.1F
37. The shape of water molecule is a. angular b. tetraheral c.
pyramidal d. linear
38.The quantity of petrol obtained from crudeoil can be increased by
redistilling the heavier fractions b. condensing the lighter fractions
polymerizing the lighter fractions d. cracking the heavier

 

39. If an excess of liquid hydrocarbon is poured into a jar of chlorine and
the sealed jar is then exposed for several hours to bright sunlight, all
the chlorine gas is consumed. The hydrocarbon is said to have undergone.
(a) apoly merization reaction (b) an addition reaction (c) a substitution
reaction (d) a reduction reaction
(a) Propanamide (b) Propanamine (c) Amino propane (d) Ammonia
Proponoic acid
40. Which of these Homolygnos has the small of sh or shy odour?
(a) alkanois (b) Aminos (c) Alkanoates (d) Ether
41.A carbon hydrocarbons consists of 92.35% carbon. If its vapour density
is 39,determine its molecular formular. a.C
H b.C H c.CH d.C H
42. A solutions of sodium trioxocarbonate (iv) contains 10.6g in 250cm
of
solution. Calculate the concentration of the solution. [Na
CO = 106.0]
A. 0.4mol dm B. 1.0moldm C. 10.6moldm D. 25.0moldm
43. Iron is paramagnetic because a. its orbitals have few unpaired
electrons b. its orbitals have only paired electrons c. iron has large
number of unpaired electrons d. it is ferromagnetic
44. Zinc is not regarded as a transitional metal even though it is a d-block
element because
3 3 6 6 9 9.
3
2 3
-3 -3 -3 -3
a. it has no electron in 3 d-block b. it has all 3 d-orbitals completely lled
c.it blends with other neighbouring elements d. it does not form complex
ion like others.
45. Dehydration of carbohydrate by concentrated H
SO will give (a) black
residue of carbon (b) the components monosaccharides (c) sooth of coal
(d) a yellow – brown known as caramel.
2

 

46. Which of the following is used for the removal of impurities from
bauxite? (a)Na AIF (b) NaOH (c) H SO (d) CaCO
47. Consider the reaction represented by the following equation:
H-CºC-H
X
Y; X and Y respectively are
A. ethene and ethane B. ethane and ethane C. ethyne and ethane D.
ethane and propene
3 6 2 4 3
H2
H2
50. The alkanoate CH CH COOC H is the product of the reaction
between:
(a) ethanoic acid and ethanol
(b) ethanoic acid and propanol
(c) propanoic acid and ethanol
(d) propanoic acid and propanol

 

 

THEORY
ATTEMPT ANY FOUR QUESTIONS
1.
A
B
C
D
F
G
H
I
J
K
L
N
O
P
Q
R
S
T
a. Give the letter representing
the strongest oxidizing agent
the strongest reducing agent
a noble gas
an element which forms a +2 ion
an element which forms a +3 ion
b. Write the formula of the compound formed between
F and H
K and Q
c. If the electronic conguration of an ion Q
is 1s 2s 2p ,give the
i. atomic number of Q
II. formula of the chloride of Q
Iii .reason why Q is described as an s-block element.
(1mk each)

 

An element X belongs to the same group as sodium but is more
reactive.
Suggest with reasons whether X would be an oxidizing agent or a reducing
agent.(1mk)
What would be a suitable method of storing X in the Laboratory?(1mk)
Describe briey what would be observed if a small piece of X were
dropped into a trough of cold water which had been coloured with red
litmus.(2mks)
Write an equation to show how an oxide of X would react with dilute HCl.
(1mk)
bi. State Faraday’s second law of electrolysis.(1mk)
ii. Draw and label a simple cell for the electrolytic purication of copper.
(2mks)
iii. Write an equation for the reaction at each electrode in the
electrolysis of copper.(2mks)
3. ai. List the two products formed when ethyne burns completely in air.
(1mk)
ii. Give the name and structural formula of the second member of the
alkyne series.(2mks)
iii. Name the type of reaction involved in the conversion of ethanol to
ethene
ii. chloroethane iii. ethanoic acid.(1/2mk each)
What is meant by each of the following terms?
i. saponication (1mk)
ii. Esterication (1mk)
d. List three properties of elements which increase generally across a
period in the periodic table. (11/2mks).

 

 

e. Give two dierences between a chemical reaction and a nuclear
reaction.(2mks)
4.a. i. Calculate the Solubility of Na CO at 25 C, If 20cm3 of its saturated
solution at that temperature gave 1.75g of the anhydrous salt. (C=12,0=16,Na=23)
List three types of salts
What types of salts are ALUMS?
State the function of Alum in water treatment plant.
b. Consider the following reaction at equilibrium:
PCl ¬?PCl +Cl
ÄH=+95kJmol
2 3 0
5 3(g) 2(g)
-1
Write an expression for the equilibrium constant K
Predict the eect of each of the following on the equilibrium position
1. increased pressure
2. increased temperature
3. removal of chlorine
e i. Using equations only, show the processes involved in the extraction
of ion and the removal of impurities in the blast furnace.
5a. Write a short note on iron
b. state 4 physical and chemical properties of iron
c. State the types of iron and their uses
d. Mention the methods used in preventing rusting of iron
7a. Explain the following;
i. Detergents
ii. soap
iii. Emulsifying Action of soap
iv. Cleansing Action of soap
v. soapless synthetic detergent
b. state the advantages and disadvantages of soap detergent
c. state the advantages and disadvantages of soapless synthetic detergent
6a. Write a short note on fats and oil
b. state the classifications of fatty acids
c. Explain 4b above
d. Mention three uses of fats and oil

8a. What are the ethical ,social and legal issues in chemistry
b. List and explain the wrong applications of chemistry
c. what are the implications of wrong application of chemistry
d. state 4 roles of the government in preventing chemical degradation.