Stoichiometric relationships (First test)

For each question choose the answer you consider to be the best.

1. How many molecules are present in 27.0 g of distilled water? (Avogadro’s constant = 6 x 10²³ mol^-1)

A. 2.7 x 10²⁴

B. 1.5

C. 9.0 x 10²³

D. 4.5

2. What amount of carbon dioxide (in mol) will be formed when 32.0 g of methane, CH₄, burns
completely in oxygen?

A. 1.0

B. 2.0

C. 4.0

D. 8.0

3. How many oxygen atoms are present in 0.5 mole of pentahydrated copper(II) sulfate, CuSO₄.5H₂O?
(Avogadro’s constant = 6 x 10²³ mol^-1)

A. 2.5

B. 4.5

C. 3.0 x 10²³

D. 2.7 x 10²⁴

4. What is the total number of atoms in 3.0 molecules of propanone, CH₃COCH₃?
(Avogadro’s constant = 6 x 10²³ mol^-1)

A. 10

B. 30

C. 1.8 x 10²⁴

D. 1.8 x 10²⁵

5. Which contains the same number of ions as the value of Avogadro’s constant?

A. 0.5 mol KBr

B. 0.5 mol CaBr₂

C. 1.0 mol CaO

D. 1.0 mol K₂O

6. Which molecular formulas are possible for a compound which has an empirical formula of C₂H₄O?

I. CH₃CH₂OH

II. CH₃CH₂CH₂COOH

III. CH₃CH₂COOCH₃

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

7. Which compound has the empirical formula with the largest mass?

A. CH₄

B. C₂H₄

C. C₂H₆

D. C₆H₆

8. What is the maximum mass, in grams, of magnesium oxide that can be formed when 4.8 g of magnesium
reacts with oxygen?

A. 4.8

B. 8.0

C. 11.2

D. 12.8

9. Which is a correct statement about the molecular formula of a compound?

A. It shows which functional groups are present in the molecule.

B. It shows how all the atoms are bonded in a molecule.

C. It is the simplest ratio of the atoms of different elements in the molecule.

D. It is an integral multiple of the empirical formula.

10. 98 g of a pure hydrocarbon contains 84 g of carbon. Which statements are correct?

I. The compound has an empirical formula of CH₂.

II. The compound has a molecular formula of C₇H₁₄.

III. Not enough information has been given to deduce the molecular formula.

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

11. 32 g of a metal, M, reacts with 8 g of oxygen to form an oxide. The formula of the oxide is MO.
What is the atomic mass of M in g mol^-1?

A. 16

B. 32

C. 64

D. 128

12. What is the maximum mass of iron, in tonnes, that can be obtained when 40 tonnes of iron(III) oxide,
Fe₂O₃ (M_r = 160), are reduced in a blast furnace according to the equation below?

Fe₂O₃ + 3CO → 2Fe + 3CO₂

A. 14

B. 28

C. 56

D. 80

13. Which factors explain why a real gas does not behave like an ideal gas at low temperatures and high pressure?

I. The volume occupied by the gaseous molecules is not negligible compared to the volume of the gas.

II. The attractive forces between the molecules affect the pressure exerted by the gas .

III. The kinetic energy of a real gas is different to the kinetic energy of an ideal gas at the same temperature.

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

14. What is the maximum amount of methanol, in mol, that could be formed when 4 mol of carbon dioxide
and 6 mol of hydrogen gas are placed in a container and react according to the equation below?

CO₂(g) + 3H₂(g) → CH₃OH(l) + H₂O(l)

A. 1

B. 2

C. 3

D. 4

15. When the equation for the complete combustion of two mol of propyne, C₃H₄, is balanced what is the sum
of all the coefficients?

2C₃H₄(g) + __ O₂(g) → __ CO₂(g) + __ H₂O(l)

A. 16

B. 18

C. 20

D. 22

16. 1 mol of any gas occupies 24 dm³ at room temperature and pressure.
When 32 g of methane burn completely in oxygen at room temperature and pressure what volume
of carbon dioxide, in dm³, will be formed?

A. 16

B. 24

C. 32

D. 48

17. What volume of ammonia, in dm³, can be made from 30 dm³ of nitrogen and 60 dm³ of hydrogen?
Assume that all volumes are measured at the same temperature and pressure and that
the reaction goes to completion according to the equation:

N₂(g) + 3H₂(g) → 2NH₃(g)

A. 40

B. 60

C. 90

D. 180

18. Ethane burns in oxygen according to the equation below. What volume of oxygen, in dm³,
reacts with 0.8 dm³ of ethane?

2C₂H₆(g) + 7O₂(g) → 4CO₂(g) + 6H₂O(l)

A. 0.8

B. 1.6

C. 2.8

D. 5.6

19. Which solution contains the most amount of sodium hydroxide?

A. 10.0 cm³ of 0.700 mol dm^-3 NaOH

B. 20.0 cm³ of 0.600 mol dm^-3 NaOH

C. 30.0 cm³ of 0.500 mol dm^-3 NaOH

D. 40.0 cm³ of 0.400 mol dm^-3 NaOH

20. Which is a correct statement about solutions?

A. When cholesterol dissolves in fat, cholesterol is the solute and fat is the solvent.

B. The concentration of a solution is the amount of solvent dissolved in 1 dm³ of solution.

C. A 1.00 mol dm^-3 solution of sodium hydroxide contains 4 g of sodium hydroxide in 1 dm³ of water.

D. In a solution of sodium chloride in water, sodium chloride is the solvent and water is the solute.

Answers

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