Stoichiometric relationships (Second test)

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

1. What amount of atoms, in mol, is present in 128 g of sulfur dioxide? (Avogadro’s constant = 6 x 10²³ mol^-1)

A. 1.2 x 10²⁴

B. 3.6 x 10²⁴

C. 2

D. 6

2. Which is the correct expression for converting the mass of a substance in grams to the
amount in moles?

A. mass ÷ molar mass

B. 1 ÷ molar mass

C. mass x molar mass

D. molar mass ÷ mass

3. Which sample of fluorine gas, F₂, contains the greatest number of fluorine molecules? (Avogadro’s constant = 6 x 10²³ mol^-1)

A. 1.9 x 10²³ F₂ molecules

B. 1.9 dm³ of F₂ at 273 K and 1.00 x 10⁵ Pa pressure

C. 1.9 g F₂

D. 1.9 mol F₂

4. What is the total number of ions present in the formula Na₂SO₄?

A. 2

B. 3

C. 4

D. 6

5. Which sample contains the least number of atoms?

A. 2 mol of NaCl

B. 2 mol of NH₃

C. 1 mol of CH₃COOH

D. 1 mol of H₂O

6. Which has the same value as Avogadro’s constant?

A. Number of electrons in 1 mol of hydrogen gas

B. Number of ions in 1 mol of molten sodium chloride

C. Number of atoms in 1 mole of helium gas

D. Number of protons in 1 mol of argon gas

7. A compound has a molar mass of approximately 56 g mol^-1. Which compound might this be?

A. AlP

B. AgOH

C. F₂O

D. MgS

8. Which statement defines molecular formula?

A. The number of atoms present in one molecule of a compound

B. The number of elements present in one molecule of a compound

C. The number of atoms of each element in one molecule of a compound

D. The simplest ratio of the numbers of atoms of each element in a molecule of a compound

9. Which sample has the greatest mass? (Avogadro’s constant = 6 x 10²³ mol^-1)

A. 1 mole of Na₂S

B. 3.0 x 10²⁴ molecules of O₂

C. 8.8 x 10¹ g of NaCl

D. 1.2 x 10²⁴ atoms of K

10. What would be the empirical formula of a hypothetical compound that contains 60% by mass
of element A (A_r = 10 ) and 40% by mass of element B (A_r = 20)?

A. A₃B₂

B. AB₃

C. AB₂

D. A₃B

11. A compound has a relative molecular mass of 74. Which are possible formulas for the
compound?

I. CH₃CH₂CH₂CH₂OH

II. CH₃CH₂CH(OH)CH₃

III. (CH₃)₃COH

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

12. What is the sum of all the coefficients when the equation for the reaction of 1 mol of
potassium metal with water is balanced?

K(s) + __ H₂O(l) → __ KOH(aq) + __ H₂(g)

A. 2.5

B. 3.5

C. 5

D. 7

13. Which change does not involve the gaseous state?

A. subliming

B. melting

C. condensing

D. evaporating

14. When calcium carbonate is heated it decomposes according to the equation:

CaCO₃(s) → CaO(s) + CO₂(g)

When 60 g of calcium carbonate is heated, 16.8 g of calcium oxide are formed. What is
the percentage yield?

A. 16.8%

B. 25%

C. 50%

D. 60%

15. Assuming that all volume are measured at the same temperature and pressure and the reaction
goes to completion what volume of ammonia, in cm³, can be prepared by reacting 20 cm³
of nitrogen gas with 30 cm³ of hydrogen gas?

N₂(g) + 3H₂(g) → 2NH₃(g)

A. 20

B. 30

C. 40

D. 50

16. The equation for the complete combustion of methylpropane is

2CH₃CH(CH₃)CH₃(g) + 13O₂(g) → 8CO₂(g) + 10H₂O(l)

What amount, in mol, of carbon dioxide will be formed when three moles of
methylpropane are combusted completely?

A. 4

B. 8

C. 12

D. 16

17. 10 cm³ of carbon monoxide and 10 cm³ of oxygen are mixed together at the same temperature
and pressure. What will be the total volume of gas present, in cm³, after they have reacted,
assuming that the volume is measured at the same temperature and pressure?

2CO(g) + O_2(g) → 2CO₂(g)

A. 10

B. 15

C. 20

D. 25

18. Which solution contains 0.2 mol of potassium hydroxide, KOH?

A. 1 cm³ of 0.2 mol dm^-3 KOH(aq)

B. 10 cm³ of 0.2 mol dm^-3 KOH(aq)

C. 100 cm³ of 2.0 mol dm^-3 KOH(aq)

D. 1 dm³ of 2.0 mol dm^-3 KOH(aq)

19. What volume, in cm³, of 0.200 mol dm^-3 sodium hydroxide solution, NaOH(aq), is required
to neutralise exactly 25.0 cm³ of 0.100 mol dm^-3 sulfuric acid solution, H₂SO₄(aq)?

A. 12.5

B. 25.0

C. 50.0

D. 100

20. What will be the concentration, in mol dm^-3, of the resulting solution when 200 cm³ of
0.200 mol dm^-3 hydrochloric acid, HCl(aq) are mixed with 300 cm³ of 0.100 mol dm^-3 HCl(aq)?

A. 0.140

B. 0.300

C. 0.070

D. 0.150

Answers

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