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WAEC questions for "Chemistry :: Stoichiometry and Chemical Reactions"
Q1

Consider the reaction represented by the equation: 2NaHCO3→Na2CO3 + H2O + CO2. What is the mass of sodiumtrioxocarbonate (IV) produced by the complete decomposition of 33.6gof sodium hydrogentrioxocarbonate (IV)? [NaHCO3= 84, Na2CO3= 106]

A

10.6g

B

16.8g

C

21.2g

D

42.4g

E
Q2

What is the percentage by weight of calcium in Ca(OCl)2? [Ca = 40, Cl = 35.5, O = 16]

A

28.0%

B

31.6%

C

43.8%

D

44.5%

E
Q3

What is the mass of 6.02 x 1024 atoms of magnesium? [Mg = 24, Avogadro's constant = 6.02 x 1023 atoms mol-1]

A

240g

B

24g

C

2.4g

D

0.24g

E
Q4

Which of the following compounds with the corresponding masses contain the highest percentage of nitrogen? [n = 14]

A

NH3 = 17

B

NH4Cl = 53.5

C

NH4NO3 = 80

D

(NH3)2SO4 = 132

E
Q5

If 5.00cm3 of 0.20mol dm-3 Na2CO3 was dilute with distilled water to obtain 250cm3 solution. What is the concentration of the resulting solution?

A

0.004mol dm-3

B

0.02mol dm-3

C

0.20mol dm-3

D

0.40mol dm-3

E
Q6

148g of salt (z) dissolved in 250cm3 of distilled water gives a concentration of 0.08mol dm-3 . Calculate the molar salt (z)

A

13.5g mol-1

B

18.5g mol-1

C

47.4g mol-1

D

74.0g mol-1

E
Q7

What is the empirical of a hydrocarbon containing 0.08moles of carbon and 0.32moles of hydrogen?

A

CH2

B

CH3

C

CH4

D

C2H4

E
Q8

If a mole of sodium caontains 6 x 1023atoms, how many atoms are contained in 0.6g of sodium? [Na = 23]

A

1.56 x 1023

B

1.56 x 1022

C

3.6 x 1023

D

3.6 x 1022

E
Q9

If 20cm3 of distilled water is added to 80cm3of 0.50mol dm-3hydrochloric acid, the concentration of the acid will be

A

0.10mol dm-3

B

0.20mol dm-3

C

0.40mol dm-3

D

2.00mol dm-3

E
Q10

Which fo the following gases will have the lowest rate of diffusion under the same conditionss? [N = 14, O = 16, Cl = 35.5, Ar = 40]

A

Argon

B

Chlorine

C

Nitrogen

D

Oxygen

E
Q11

What volume of hydrogen will be produced when 48g of magnesium reacts comlpetely with dilute hydrochloric acid according to the following equation?

Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) [Mg = 24, 1 mole of hydrogen occupies 22.4dm3 at s.t.p]

A

11.2dm3

B

22.4dm3

C

33.6dm3

D

44.8dm3

E
Q12

Determine the mass of copper deposited by 4.0 moles of electrons in the reaction represented by the equation below. Cu(aq)2+ + 2e- → Cu(s)

A

32

B

64

C

128

D

256

E
Q13

What volume of hydrogen would be left over when 300cm3 of oxygen and 1000cm3 of hydrogen are exploded in a sealed tube? [2H2(g) + O2(g) 2H20(g)]

A

200cm3

B

400cm3

C

600cm3

D

700cm3

E
Q14

What quantity of electrons (in moles) is needed to discharge two moles of aluminium from aluminium oxide (Al2O3)?

A

1

B

2

C

4

D

6

E
Q15

The mass of 800cm3 of gas X at s.t.p is 1.0g. What is the molar mass of X? [1 mole of gas at s.t.p occupies 22.4dm3]

A

18.0g mol-1

B

22.4g mol-1

C

28.0g mol-1

D

36.0g mol-1

E
Q16

If 60cm3 of gas is heated from 27C to 50C, what is the new volume of the gas at constant pressure?

A

32.4cm3

B

55.7cm3

C

64.6cm3

D

111.1cm3

E
Q17

If 11g of gas occupies 5.6dm3 at s.t.p. Calculate its vapour density. [1.0 mole of a gas occupies 22.4dm3 at s.t.p]

A

22

B

4

C

66

D

88

E
Q18

Which of the following quantities is the same for one mole of Br2(l) and one mole of He(g)?

A

Number of molecules

B

Number of atoms

C

Total mass of the particle

D

Volume occupied at s.t.p

E
Q19

If 100cm3 of hydrogen diffused through a porous pot in 1.0 second, how will it take the same volume of oxygen to diffuse through the same pot under the same conditions? [H = 1.0; O = 16]

A

2.5s

B

4.0s

C

16.0s

D

25.0s

E
Q20

The pH of 0.50mol dm3 solution of HCl, H2SO4 and CH3COOH were measured. Which of the following statements about values obtained is correct?

A

The pH value was equal to 5 in each case

B

The pH value of the HCl and H2SO4 solutions were equal

C

Their pH values added up to 14

D

The pH value of the CH3COOH was the highest

E
Q21

What volume of 0.20 mol dm-3 NaOH solution would yield 5.0g of NaOH on evaporation to dryness? [NaOH = 40g mol-1]

A

400cm3

B

625cm3

C

1000cm3

D

1600cm3

E
Q22

What volume of hydrogen will be produced if 100cm3 of ammonia is completely decomposed at constant temperature and pressure? The equation for the reaction is 2NH3(g) → N2(g) + 3H2(g)

A

50cm3

B

150cm3

C

200cm3

D

300cm3

E
Q23

Calculate the mass of chlorine gas which occupies a volume of 1.12dm3 at s.t.p. [Cl = 35.5; 1 mole of gas occupies 22.4dm3 at s.t.p]

A

1.80g

B

3.55g

C

7.10g

D

15.5g

E
Q24

Determine the mass of sulhpur (IV) oxide obtained when 91.0g of oxygen reacts completely with sulphur according to the following equation: S(s) + O2(g) → SO2(g) [S = 32; 0=16]

A

123g

B

139g

C

155g

D

182g

E
Q25

Calculating the mass of sodium hydroxide in 5.00dm3 of a 0.125mol dm-3 solution. [NaOH = 40g mol-1]

A

0.156g

B

0.625g

C

1.00g

D

25.0g

E
Q26

Calculate the mass of ZnSO4 produced when excess ZnCO3 is added to 50.0cm3 of 4.00mol dm-3 H2SO4 . The equation of the reaction is:ZnCO3 + H2SO4 → ZnSO4 + CO2 + H2O [ZnSO4 = 161gmol-1]

A

0.20g

B

1.29g

C

32.2g

D

39.0g

E
Q27

9.60g of a gas X occupies the same volume as 0.30g of hydrogen under the same condition. Calculate the molar mass of X. [H = 1]

A

8g mol-1

B

16g mol-1

C

32g mol-1

D

64g mol-1

E
Q28

One mole of a compound M(HCO3)2 has a mass of 162g. Calculate the relative atomic mass of M.[H = 1, C = 12, O = 16]

A

122

B

101

C

53

D

40

E
Q29

What mass of copper would be deposited by a current of 1.0 ampere passing for 965 seconds through copper (II) tetraoxosulphate (VI) solution? [Cu = 63.5; 1F = 96500C]

A

0.318g

B

0.635g

C

3.18g

D

6.35g

E

9.65g

Q30

What is the percentage by mass of sulphur in Al2(SO4)3? [ Al2(SO4)3 = 342gmole-1, S = 32]

A

9.36%

B

14.7%

C

21.33%

D

28.07%

E

42.66%

Q31

Which of the following is the relative molecular mass of a compund which has empirical formular CH2O? [H = 1, C = 12, O = 16]

A

42

B

45

C

126

D

145

E

180

Q32

What volume of carbon (IV) is produced at s.t.p when 2.50g of CaCO3 react with excess acid according to the following equation? CaCO3 + 2HCl → CaCl2 + H2O + CO2 [CaCO3 = 100;molar volume of a gas at s.t.p = 22.4dm3]

A

11.20dm3

B

5.60dm3

C

2.24dm3

D

0.56dm3

E

0.28dm3

Q33

What amount of copper is deposited when 13.0g of zinc reacts with excess copper (II) tetraoxosulphate (VI) solution according to the following equation?

Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s) [Cu = 63.5, Zn = 65]

A

0.1 mole

B

0.2 mole

C

0.3 mole

D

0.4 mole

E

0.5 mole

Q34

What is the percentage by mass of copper in copper (I) (Cu2O) ? (O = 16, Cu = 64)

A

88.9%

B

80.0%

C

66.7%

D

20%

E

11.1%

Q35

what mass of copper will be deposited by the liberation of Cu2+ when 0.1F of electricity flows through an aqueous solution of a copper (II) salt? (Cu = 64)

A

64g

B

32g

C

12.8g

D

6.4g

E

3.2g

Q36

What is the amount (in moles) of of hydrogen gas that would be produced if 0.6 mole of hydrochloric acid reacts with excess zinc according to the following equation?

Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)

A

0.1 mole

B

0.2 mole

C

0.3 mole

D

1.0 mole

E

2.9 mole

Q37

In any chemical reaction, the total mass of the products is always equal to that of the reactants. This statement of the law of

A

definite matter

B

conservation of matter

C

multiple proportions

D

reciprocal proportions

E

constant composition

Q38

The number of atoms in 1.2g of carbon-12 isotope is

A

1.00 X 1022

B

6.02 X 1022

C

1.02 X 1023

D

1.00 X 1024

E

6.02 X 1024

Q39

Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g). From the equation above, what mass of hydrogen would be produced if 12.0g of magnesium reacted completely with dilute hydrochloric acid? (H = 1, Mg = 24)

A

1.0g

B

2.0g

C

6.0g

D

12.0g

E

24.0g

Q40

What is the molar mass of an alkyne with the formula CxH14? (H = 1, C = 12)

A

86g

B

92g

C

98g

D

110g

E

112g

Q41

What volume of distilled water should be added to 400cm3 of 2.0 mole dm-3 H2SO4 to obtain 0.20 mole dm-3 of solution?

A

600cm3

B

800cm3

C

1,000cm3

D

3,600cm3

E

4,000cm3

Q42

What volume of propane is left unreacted when 20cm3 of oxygen and 20cm3 of propane react according the following equation? C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)

A

4cm3

B

5cm3

C

14cm3

D

15cm3

E

16cm3

Q43

What is the number of oxygen atoms in 32g of the gas? (O = 16, L = 6.0 x 1023mol-1)

A

3.2 x 1023

B

6.0 x 1023

C

1.2 x 1024

D

1.6 x 1024

E

2.0 x 1024

Q44

What is the amount (in moles) of sodium trioxocarbonate (IV) in 5.3g of the compound? (Na2CO3 = 106)

A

0.05

B

0.10

C

0.20

D

0.50

E

2. 00

Q45

A compound which liberates carbon (IV) oxide from a hydrogentrioxocarbonate (IV) could have the molecular formula

A

C2H5OH

B

C3H4

C

HCOOH

D

H2O2

E

C6H6

Q46

2NaNO3 → 2NaNO2 + O2 From the equation above, what is the volume of oxygen produced at s.t.p when 8.5g of NaNO3 is heated until no further gas is evolved? (NaNO3 = 85, molar volume of gas at s.t.p = 22.4dm3 )

A

1.12dm3

B

2.24dm3

C

4.48dm3

D

11.2dm3

E

22.4dm3

Q47

Compounds that have the same molecular formular but different structures are said to be

A

allotrophic

B

polymophic

C

polymeric

D

isomeric

E

isotopic

Q48

How many molecules are ther in 14g of Hydrogen gas at s.t.p? (N = 14, Avogadro Number = 6.0 X 1023mol-1)

A

1.2 X 1023

B

3.0 x 1023

C

6.0 x 1023

D

1.2 x 1024

E

3.0 x 1024

Q49

How many mole(s) of AgNO3 are there in 500cm3 o 0.01M AgNO3 solution?

A

0.005 mole

B

0.05 mole

C

0.5 mole

D

1 mole

E

5 moles

Q50

If 3 moles of electron are required to deposit one mole of metal, M during which the electrolysis of its molten chloride, the empirical formular of its metallic chloride is

A

M3Cl

B

M3Cl2

C

MCl

D

M2Cl3

E

MCl3

Q51

120cm3 of hydrogen were sparked with 60cm3 of oxygen at 110oC. What was the volume of steam produced? The equation for the reaction is 2H2(g) + O2(g) → 2H2O(g)

A

30cm3

B

60cm3

C

90cm3

D

120cm3

E

180cm3

Q52

If 200cm3 of gas at s.t.p has a mass of 0.268g. What is its molar mass? (Molar volume of a gas at s.t.p = 22.4dm3 )

A

300g

B

200g

C

150g

D

30g

E

15g

Q53

Given the following half-cell reaction: 2Cl(aq) → Cl2(g) + 2e. How many moles of electrons will be required to produce 1.12dm3 of chlorine gas at s.t.p? (Molar volume of a gas at s.t.p = 22.4dm3)

A

1.00

B

4.00

C

0.20

D

0.10

E

0.01

Q54

Given that 1 mole of carbon-12 weighs 12.0g. How many atoms are there in 24.0g magnesium? (C = 12, Mg = 24, NA = 6.02 x 1023mol-1)

A

x 6.02 x 1023

B

1x 6.02x1023

C

2 x 6.02 x 1023

D

3 x 6.02 x 1023

E

4 x 6.02 x 1023

Q55
Given that 32.0g of sulphur contains 6.02x10 sulphur atoms, how many atoms are there in 2.70g of aluminum? (Al=27, S=32)
A
6.02x10
B
3.01x10
C
6.02x10
D
5.08x10
E
3.01x10
Q56

What volume of oxygen will be left unreacted when a mixture of 100cm3 of hygrogen and 200cm3 of oxygen are exploded in a eudiometer?

A

300cm3

B

200cm3

C

150cm3

D

100cm3

E

50cm3