Atoms, Molecules and Stoichiometry Exam-style MCQs | A-Level Chemistry CIE

Question 1

Sodium hydroxide neutralises acid.

H⁺ + OH^- ➔ H₂O

In a 11,000 dm³ sample of an aqueous solution, the concentration of acid, [H⁺], is 1.26 × 10^-3 moldm^-3.

Which mass of solid sodium hydroxide neutralises the acid?

A

0.0214 g

B

0.0504 g

C

236 g

D

554 g

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Question 2

The relative atomic mass is defined as

A

the mass of an atom of an element relative to 1/12^th the mass of a carbon-12 atom

B

the mass of an atom of an element relative to the mass of a hydrogen atom

C

the average mass of an element relative to 1/12^th the mass of a carbon atom

D

the average mass of an atom of an element relative to 1/12^th the mass of a carbon-12 atom

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Question 3

A student mixes 100 cm³ of 0.200 mol dm^-3 NaCl_(aq) with 100 cm³ of 0.200 mol dm^-3 Na₂CO_3(aq).

What is the total concentration of Na⁺ ions in the mixture formed?

A

0.100 mol dm^-3

B

0.200 mol dm^-3

C

0.300 mol dm^-3

D

0.400 mol dm^-3

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Question 4

Sodium reacts with water as shown below.

2Na_(s) + 2H₂O_(l) ➔ 2NaOH_(aq) + H_2(g)

Which mass of sodium reacts with water to produce 960 cm³ of hydrogen gas at RTP?

A

0.46 g

B

0.92 g

C

1.84 g

D

3.68 g

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Question 5

What is the number of oxygen atoms in 88.0 g of CO₂?

A

3.01 × 10²³

B

1.20 × 10²⁴

C

2.41 × 10²⁴

D

4.82 × 10²⁴

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Question 6

What is the empirical formula of an oxide of nitrogen that contains 26% nitrogen by mass?

A

NO₂

B

N₂O₃

C

N₂O₅

D

N₄O₅

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Question 7

30 cm³ of xenon are mixed with 20 cm³ of fluorine. The gases react according to the following equation. Assume that the temperature and pressure remain constant.

Xe_(g) + F_2(g) ➔ XeF_2(g)

What is the final volume of gas after the reaction is complete?

A

50 cm³

B

40 cm³

C

30 cm³

D

20 cm³

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Question 8

In a car airbag, sodium azide (NaN₃) decomposes to form sodium metal and nitrogen gas.

2NaN_3(s) ➔ 2Na_(s) + 3N_2(g)

The sodium metal then reacts with potassium nitrate to produce more nitrogen gas.

10Na_(s) + 2KNO_3(s) ➔ N_2(g) + 5Na₂O_(s) + K₂O_(s)

If 2.00 mol of sodium azide react in this way, how many molecules of N₂ will be formed?

The Avogadro constant, L = 6.022 x 10²³ mol⁻¹.

A

2.41 x 10²⁴

B

1.93 x 10²⁴

C

1.81 x 10²⁴

D

9.63 x 10²³

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Question 9

A 20.0 cm³ sample of a 0.400 mol dm^-3 aqueous solution of a metal bromide (MBr_n) reacts exactly with 160 cm³ of 0.100 mol dm^-3 aqueous silver nitrate.

What is the formula of the metal bromide?

A

MBr

B

MBr₂

C

MBr₃

D

MBr₄

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Question 10

What is the mass, in mg, of carbon formed when 3.0 × 10^-3 mol of propene undergoes incomplete combustion?

2C₃H₆ + 3O₂ ➔ 6C + 6H₂O

A

9.0 × 10^-3

B

3.6 × 10^-2

C

1.08 × 10²

D

2.16 × 10²

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Question 11

The equation for the reaction between zinc and hydrochloric acid is

Zn + 2HCl ➔ ZnCl₂ + H₂

What is the minimum mass, in mg, of zinc (A_r = 65.4) needed to react with 50.0 cm³ of 1.68 mol dm^-3 hydrochloric acid?

A

2.75

B

5.49

C

2.75 × 10³

D

5.49 × 10³

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Question 12

A student is provided with 5.00 cm³ of 1.00 mol dm^-3 ammonia solution. The student was asked to prepare an ammonia solution with a concentration of 0.050 mol dm^-3

What volume of water should the student add?

A

45.0 cm³

B

95.0 cm³

C

100 cm³

D

995 cm³

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Question 13

Nitration of 1.70 g of methyl benzoate (M_r = 136.0) produces methyl 3-nitrobenzoate (M_r = 181.0). The percentage yield is 65.0%

What mass, in g, of methyl 3-nitrobenzoate is produced?

A

0.830

B

1.10

C

1.47

D

2.26

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Question 14

Which sample, measured at room temperature and pressure, contains the greatest number of the stated particles?

A

1 g of hydrogen molecules

B

1 g of helium atoms

C

1 dm³ of hydrogen molecules

D

1 dm³ of helium atoms

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Question 15

5.0 g of an oxide of molybdenum contain 4.0 g of molybdenum.

What is the empirical formula of this oxide?

A

MoO₂

B

Mo₄O₅

C

Mo₂O₃

D

Mo₃O₂

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Question 16

What is the percentage yield when 20 g of aluminium are produced from 50 g of aluminium oxide?

2Al₂O₃ ➔ 4Al + 3O₂

A

76%

B

40%

C

33%

D

19%

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