Stoichiometry Quiz

Duration: 45 Minutes Total Marks: 30

Section A: Multiple Choice (5 Marks)

  1. What is the relative formula mass ($M_r$) of $\text{Ca(OH)}_2$?
    ($A_r$: $\text{Ca} = 40, \text{O} = 16, \text{H} = 1$)
    A. 58
    B. 74
    C. 82
    D. 90

  2. Which of the following represents the correct molar gas volume at r.t.p.?
    A. 1 mole = $22.4\text{ dm}^3$
    B. 1 mole = $24\text{ dm}^3$
    C. 1 mole = $24,000\text{ cm}^3$
    D. Both B and C

  3. A compound has an empirical formula of $\text{CH}_2$ and a relative molecular mass ($M_r$) of 56. What is its molecular formula?
    ($A_r$: $\text{C} = 12, \text{H} = 1$)
    A. $\text{C}_2\text{H}_4$
    B. $\text{C}_3\text{H}_6$
    C. $\text{C}_4\text{H}_8$
    D. $\text{C}\text{H}_2$

  4. Which substance is the limiting reactant if 2 moles of $\text{H}_2$ and 2 moles of $\text{O}_2$ react to form $\text{H}_2\text{O}$?
    Equation: $2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}$
    A. $\text{H}_2$
    B. $\text{O}_2$
    C. $\text{H}_2\text{O}$
    D. Neither

  5. What is the mass of 0.5 moles of $\text{NaCl}$?
    ($A_r$: $\text{Na} = 23, \text{Cl} = 35.5$)
    A. 29.25 g
    B. 58.5 g
    C. 117 g
    D. 23 g

Section B: Short Answer (15 Marks)

  1. Write a balanced symbol equation, including state symbols, for the reaction between aqueous sodium hydroxide and aqueous sulfuric acid. (3 Marks)

  2. Calculate the percentage by mass of nitrogen in ammonium nitrate, $\text{NH}_4\text{NO}_3$. (4 Marks)
    ($A_r$: $\text{N} = 14, \text{H} = 1, \text{O} = 16$)

  3. A student reacts 2.4 g of magnesium with excess hydrochloric acid.
    $$\text{Mg}(s) + 2\text{HCl}(aq) \rightarrow \text{MgCl}_2(aq) + \text{H}_2(g)$$
    Calculate the volume of hydrogen gas produced at r.t.p. (4 Marks)
    ($A_r$: $\text{Mg} = 24$)

  4. Define ’empirical formula’ and explain how it differs from ‘molecular formula’. (4 Marks)

Section C: Extended Response (10 Marks)

  1. In a titration, $25.0\text{ cm}^3$ of $0.10\text{ mol/dm}^3$ sodium hydroxide ($\text{NaOH}$) is neutralized by $20.0\text{ cm}^3$ of sulfuric acid ($\text{H}_2\text{SO}_4$) of unknown concentration.
    $$2\text{NaOH}(aq) + \text{H}_2\text{SO}_4(aq) \rightarrow \text{Na}_2\text{SO}_4(aq) + 2\text{H}_2\text{O}(l)$$

    a) Calculate the number of moles of $\text{NaOH}$ used. (2 Marks)
    b) Determine the number of moles of $\text{H}_2\text{SO}_4$ that reacted. (3 Marks)
    c) Calculate the concentration of the sulfuric acid in $\text{mol/dm}^3$. (3 Marks)
    d) Convert this concentration to $\text{g/dm}^3$. (2 Marks)
    ($A_r$: $\text{H} = 1, \text{S} = 32, \text{O} = 16$)


Attempt the quiz before checking the mark scheme
Mark Scheme C3 - Stoichiometry Mark Scheme
Topic guide: C3 - Stoichiometry