Stoichiometry and quantitative chemistry: Grade 11 Past Paper Questions

QUESTION 2. Methane gas, CH₄, of mass 34,5 g is reacted with oxygen gas in a sealed container according to the following balanced chemical equation: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l). The initial volume of the oxygen gas was 69,3 dm³ when measured at STP. 2.1.1 Define the term limiting reagent. 2.1.2 Determine the limiting reagent in this reaction. 2.1.3 Determine the total number of moles of gas in the container after the reaction is completed. 2.1.4 Calculate the percentage yield of CO₂ if 58,08 g CO₂ was formed during the reaction. 2.2 The solubility of calcium nitrate is highly endothermic. A 200 cm³ solution is formed by dissolving 105,6 g Ca(NO₃)₂ in water. 2.2.1 Define concentration. 2.2.2 Calculate the concentration of this solution. 2.2.3 Calculate the number of nitrate (NO₃⁻) ions in the solution. 2.2.4 How will the temperature of the final solution be affected? Choose from INCREASES, DECREASES or REMAINS THE SAME. Explain the answer. 2.3 A 29,05 g sample of a compound contains 11,62 g carbon, 1,94 g hydrogen and 15,49 g oxygen. 2.3.1 Determine the empirical formula of this compound. 2.3.2 The molecular mass of this compound is 90 g·mol⁻¹. Determine the molecular formula of this compound.

QUESTION 1: MULTIPLE-CHOICE QUESTIONS. 1.1 A certain chloride is formed when 0,5 moles of element X combines with 1,5 moles of chlorine. Which ONE of the following is the correct empirical formula for this chloride? A. XCl B. XCl₂ C. XCl₃ D. XCl₄. 1.2 What is the volume occupied by 1 g of hydrogen gas at STP? A. 11,2 dm³ B. 22,4 dm³ C. 33,6 dm³ D. 44,8 dm³. 1.3 Which ONE of the reactions below will produce hydrogen gas? A. HCl + Mg → B. HNO₃ + Mg(OH)₂ → C. H₂SO₄ + MgCO₃ → D. CH₃COOH + MgO →

2.3 A 29,05 g sample of a compound contains 11,62 g carbon, 1,94 g hydrogen and 15,49 g oxygen. 2.3.1 Determine the empirical formula of this compound. 2.3.2 The molecular mass of this compound is 90 g·mol⁻¹. Determine the molecular formula of this compound. QUESTION 3. The following reversible reaction takes place in a closed container: A₂ + B₂ ⇌ 2AB. The graph below shows the changes in chemical potential energy during the course of the reaction. 3.1 Is the forward reaction endothermic or exothermic? Give a reason for the answer. 3.2 Calculate ΔH for the forward reaction. 3.3 Define activation energy. 3.4 What is the activation energy for the reverse reaction? 3.5 How does the strength of the bonds within the reactant molecules compare to the strength of the bonds within the product molecules for the forward reaction? Choose from STRONGER THAN, WEAKER THAN, or OF SIMILAR STRENGTH. Give a reason for the answer.