"Stoichiometry and Chemical Reactions" question number distribution across years

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

Q1

Consider the reaction represented by the equation: 2NaHCO_{3} → Na_{2}CO_{3 }+ H_{2}O + CO_{2}. What is the mass of sodiumtrioxocarbonate (IV) produced by the complete decomposition of 33.6g of sodium hydrogentrioxocarbonate (IV)? [NaHCO_{3} = 84, Na_{2}CO_{3} = 106]

A

10.6g

B

16.8g

C

21.2g

D

42.4g

E

**Answer:** D

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

**Answer:** A

Q3

What is the mass of 6.02 x 10^{24} atoms of magnesium? [Mg = 24, Avogadro's constant = 6.02 x 10^{23} atoms mol^{-1}]

A

240g

B

24g

C

2.4g

D

0.24g

E

**Answer:** A

Q4

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

A

NH_{3} = 17

B

NH_{4}Cl = 53.5

C

NH_{4}NO_{3} = 80

D

(NH_{3})_{2}SO_{4} = 132

E

**Answer:** A

Q5

If 5.00cm^{3} of 0.20mol dm^{-3} Na_{2}CO_{3} was dilute with distilled water to obtain 250cm^{3} 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

**Answer:** A

Q6

148g of salt (z) dissolved in 250cm^{3} 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

**Answer:** D

Q7

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

A

CH_{2}

B

CH_{3}

C

CH_{4}

D

C_{2}H_{4}

E

**Answer:** C

Q8

If a mole of sodium caontains 6 x 10^{23} atoms, how many atoms are contained in 0.6g of sodium? [Na = 23]

A

1.56 x 10^{23}

B

1.56 x 10^{22}

C

3.6 x 10^{23}

D

3.6 x 10^{22}

E

**Answer:** B

Q9

If 20cm^{3 }of distilled water is added to 80cm^{3} of 0.50mol dm^{-3}hydrochloric 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

**Answer:** D

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

**Answer:** A

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)} → MgCl_{2(aq)} + H_{2(g)} [Mg = 24, 1 mole of hydrogen occupies 22.4dm^{3} at s.t.p]

A

11.2dm^{3}

B

22.4dm^{3}

C

33.6dm^{3}

D

44.8dm^{3}

E

**Answer:** D

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

**Answer:** C

Q13

What volume of hydrogen would be left over when 300cm^{3} of oxygen and 1000cm^{3} of hydrogen are exploded in a sealed tube? [2H_{2(g) }+ O2_{(g) }→_{ }2H_{2}0(g)]

A

200cm^{3}

B

400cm^{3}

C

600cm3

D

700cm^{3}

E

**Answer:** C

Q14

What quantity of electrons (in moles) is needed to discharge two moles of aluminium from aluminium oxide (Al_{2}O_{3})?

A

1

B

2

C

4

D

6

E

**Answer:** D

Q15

The mass of 800cm^{3} 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 22.4dm^{3}]

A

18.0g mol^{-1}

B

22.4g mol^{-1}

C

28.0g mol^{-1}

D

36.0g mol^{-1}

E

**Answer:** C

Q16

If 60cm^{3 }of gas is heated from 27°C to 50°C, what is the new volume of the gas at constant pressure?

A

32.4cm^{3}

B

55.7cm3

C

64.6cm^{3}

D

111.1cm^{3}

E

**Answer:** D

Q17

If 11g of gas occupies 5.6dm^{3} at s.t.p. Calculate its vapour density. [1.0 mole of a gas occupies 22.4dm^{3} at s.t.p]

A

22

B

4

C

66

D

88

E

**Answer:** A

Q18

Which of the following quantities is the same for one mole of Br_{2(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

**Answer:** B

Q19

If 100cm^{3} 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

**Answer:** B

Q20

The pH of 0.50mol dm^{3} solution of HCl, H_{2}SO_{4} and CH_{3}COOH 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 H_{2}SO_{4} solutions were equal

C

Their pH values added up to 14

D

The pH value of the CH_{3}COOH was the highest

E

**Answer:** D

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

400cm^{3}

B

625cm^{3}

C

1000cm^{3}

D

1600cm^{3}

E

**Answer:** B

Q22

What volume of hydrogen will be produced if 100cm^{3 }of ammonia is completely decomposed at constant temperature and pressure? The equation for the reaction is 2NH_{3(g)} → N_{2(g) }+ 3H_{2(g)}

A

50cm^{3}

B

150cm^{3}

C

200cm^{3}

D

300cm^{3}

E

**Answer:** B

Q23

Calculate the mass of chlorine gas which occupies a volume of 1.12dm^{3} at s.t.p. [Cl = 35.5; 1 mole of gas occupies 22.4dm^{3} at s.t.p]

A

1.80g

B

3.55g

C

7.10g

D

15.5g

E

**Answer:** A

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) }+ O_{2(g)} → SO_{2(g)} [S = 32; 0=16]

A

123g

B

139g

C

155g

D

182g

E

**Answer:** D

Q25

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

A

0.156g

B

0.625g

C

1.00g

D

25.0g

E

**Answer:** D

Q26

Calculate the mass of ZnSO_{4} produced when excess ZnCO_{3} is added to 50.0cm^{3} of 4.00mol dm^{-3} H_{2}SO_{4} . The equation of the reaction is:ZnCO_{3 }+ H_{2}SO_{4} → ZnSO_{4} + CO_{2 }+ H_{2}O [ZnSO_{4} = 161gmol^{-1}]

A

0.20g

B

1.29g

C

32.2g

D

39.0g

E

**Answer:** C

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

**Answer:** D

Q28

One mole of a compound M(HCO_{3})_{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

**Answer:** D

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

**Answer:** A

Q30

What is the percentage by mass of sulphur in Al_{2}(SO_{4})_{3}? [ Al_{2}(SO_{4})_{3} = 342gmole^{-1}, S = 32]

A

9.36%

B

14.7%

C

21.33%

D

28.07%

E

42.66%

**Answer:** D

Q31

Which of the following is the relative molecular mass of a compund which has empirical formular CH_{2}O? [H = 1, C = 12, O = 16]

A

42

B

45

C

126

D

145

E

180

**Answer:** E

Q32

What volume of carbon (IV) is produced at s.t.p when 2.50g of CaCO_{3 }react with excess acid according to the following equation? CaCO_{3} + 2HCl → CaCl_{2} + H_{2}O + CO_{2} [CaCO_{3} = 100;molar volume of a gas at s.t.p = 22.4dm^{3}]

A

11.20dm^{3}

B

5.60dm^{3}

C

2.24dm^{3}

D

0.56dm^{3}

E

0.28dm^{3}

**Answer:** D

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) }+ CuSO_{4(aq) }→ ZnSO_{4(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

**Answer:** B

Q34

What is the percentage by mass of copper in copper (I) (Cu_{2}O) ? (O = 16, Cu = 64)

A

88.9%

B

80.0%

C

66.7%

D

20%

E

11.1%

**Answer:** A

Q35

what mass of copper will be deposited by the liberation of Cu^{2+} 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

**Answer:** E

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)} →_{ }ZnCl_{2(aq) }+ H_{2(g)}

A

0.1 mole

B

0.2 mole

C

0.3 mole

D

1.0 mole

E

2.9 mole

**Answer:** C

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

**Answer:** B

Q38

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

A

1.00 X 10^{22}

B

6.02 X 10^{22}

C

1.02 X 10^{23}

D

1.00 X 10^{24}

E

6.02 X 10^{24}

**Answer:** B

Q39

Mg_{(s)} + 2HCl_{(aq)} → MgCl_{2(aq)} + H_{2(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

**Answer:** D

Q40

What is the molar mass of an alkyne with the formula C_{x}H_{14? (H = 1, C = 12)}

A

86g

B

92g

C

98g

D

110g

E

112g

**Answer:** D

Q41

What volume of distilled water should be added to 400cm^{3} of 2.0 mole dm^{-3} H_{2}SO_{4 }to obtain 0.20 mole dm^{-3} of solution?

A

600cm^{3}

B

800cm^{3}

C

1,000cm^{3}

D

3,600cm^{3}

E

4,000cm^{3}

**Answer:** D

Q42

What volume of propane is left unreacted when 20cm^{3} of oxygen and 20cm^{3} of propane react according the following equation? C_{3}H_{8(g)} + 5O_{2(g) }→ 3CO_{2(g)} + 4H_{2}O_{(g)}

A

4cm^{3}

B

5cm^{3}

C

14cm^{3}

D

15cm^{3}

E

16cm^{3}

**Answer:** E

Q43

What is the number of oxygen atoms in 32g of the gas? (O = 16, L = 6.0 x 10^{23}mol^{-1})

A

3.2 x 10^{23}

B

6.0 x 10^{23}

C

1.2 x 10^{24}

D

1.6 x 10^{24}

E

2.0 x 10^{24}

**Answer:** B

Q44

What is the amount (in moles) of sodium trioxocarbonate (IV) in 5.3g of the compound? (Na_{2}CO_{3} = 106)

A

0.05

B

0.10

C

0.20

D

0.50

E

2. 00

**Answer:** A

Q45

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

A

C_{2}H_{5}OH

B

C_{3}H_{4}

C

HCOOH

D

H_{2}O_{2}

E

C_{6}H_{6}

**Answer:** C

Q46

2NaNO_{3} → 2NaNO_{2} + O_{2} From the equation above, what is the volume of oxygen produced at s.t.p when 8.5g of NaNO_{3 }is heated until no further gas is evolved? (NaNO_{3} = 85, molar volume of gas at s.t.p = 22.4dm^{3} )

A

1.12dm^{3}

B

2.24dm^{3}

C

4.48dm^{3}

D

11.2dm^{3}

E

22.4dm^{3}

**Answer:** A

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

**Answer:** D

Q48

How many molecules are ther in 14g of Hydrogen gas at s.t.p? (N = 14, Avogadro Number = 6.0 X 10^{23}mol^{-1})

A

1.2 X 10^{23}

B

3.0 x 10^{23}

C

6.0 x 10^{23}

D

1.2 x 10^{24}

E

3.0 x 10^{24}

**Answer:** C

Q49

How many mole(s) of AgNO_{3} are there in 500cm_{3 }o 0.01M AgNO_{3} solution?

A

0.005 mole

B

0.05 mole

C

0.5 mole

D

1 mole

E

5 moles

**Answer:** A

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

M_{3}Cl

B

M_{3}Cl_{2}

C

MCl

D

M_{2}Cl_{3}

E

MCl_{3}

**Answer:** E

Q51

120cm^{3} of hydrogen were sparked with 60cm^{3} of oxygen at 110^{o}C. What was the volume of steam produced? The equation for the reaction is 2H_{2(g)} + O_{2(g)} → 2H_{2}O_{(g)}

A

30cm^{3}

B

60cm^{3}

C

90cm^{3}

D

120cm^{3}

E

180cm^{3}

**Answer:** D

Q52

If 200cm^{3} 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 = 22.4dm^{3 })

A

300g

B

200g

C

150g

D

30g

E

15g

**Answer:** D

Q53

Given the following half-cell reaction: 2Cl_{(aq)} → Cl_{2(g)} + 2e. How many moles of electrons will be required to produce 1.12dm^{3 }of chlorine gas at s.t.p? (Molar volume of a gas at s.t.p = 22.4dm^{3})

A

1.00

B

4.00

C

0.20

D

0.10

E

0.01

**Answer:** D

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 10^{23}mol^{-1})

A

½ x 6.02 x 10^{23}

B

1x 6.02x10^{23 }

C

2 x 6.02 x 10^{23}

D

3 x 6.02 x 10^{23}

E

4 x 6.02 x 10^{23}

**Answer:** B

Q55

Given that 32.0g of sulphur contains 6.02x10²³ sulphur atoms, how many atoms are there in 2.70g of aluminum? (Al=27, S=32)

A

6.02x10²³

B

3.01x10²³

C

6.02x10²²

D

5.08x10²²

E

3.01x10²²

**Answer:** C

Q56

What volume of oxygen will be left unreacted when a mixture of 100cm^{3} of hygrogen and 200cm^{3 }of oxygen are exploded in a eudiometer?

A

300cm^{3}

B

200cm^{3}

C

150cm^{3}

D

100cm^{3}

E

50cm^{3}

**Answer:** C