This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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Here is the solution for Question 8: Question 8: What mass of zinc will be required to react completely with 100 cm^3 of 0.1 moldm^-3 hydrochloric acid? Determine volume of hydrogen gas that would be evolved at s.t.p. Equation of reaction: Zn_(s) + 2HCl_(aq) ZnCl_2(aq) + H_2(g) [Zn = 65, molar volume = 22.4 dm^3mol^-1] Given: Volume of HCl = 100 cm^3 = 0.1 dm^3 Concentration of HCl = 0.1 moldm^-3 Molar mass of Zn = 65 g/mol Molar volume at s.t.p. = 22.4 dm^3mol^-1 Equation: Zn_(s) + 2HCl_(aq) ZnCl_2(aq) + H_2(g) Part 1: Calculate the mass of zinc required. Step 1: Calculate the moles of hydrochloric acid (HCl). Moles of HCl = Concentration × Volume Moles of HCl = 0.1 moldm^-3 × 0.1 dm^3 Moles of HCl = 0.01 mol Step 2: Determine the moles of zinc (Zn) required using the mole ratio from the balanced equation. From the equation, 1 mol of Zn reacts with 2 mol of HCl. Moles of Zn = Moles of HCl × 1 mol Zn2 mol HCl Moles of Zn = 0.01 mol × (1)/(2) Moles of Zn = 0.005 mol Step 3: Calculate the mass of zinc required. Mass of Zn = Moles of Zn × Molar mass of Zn Mass of Zn = 0.005 mol × 65 g/mol Mass of Zn = 0.325 g Part 2: Determine the volume of hydrogen gas evolved at s.t.p. Step 1: Determine the moles of hydrogen gas (H_2) produced using the mole ratio from the balanced equation. From the equation, 2 mol of HCl produces 1 mol of H_2. Moles of H_2 = Moles of HCl × 1 mol H_22 mol HCl Moles of H_2 = 0.01 mol × (1)/(2) Moles of H_2 = 0.005 mol Step 2: Calculate the volume of hydrogen gas evolved at s.t.p. Volume of H_2 = Moles of H_2 × Molar volume at s.t.p. Volume of H_2 = 0.005 mol × 22.4 dm^3mol^-1 Volume of H_2 = 0.112 dm^3 Convert to cm^3: Volume of H_2 = 0.112 dm^3 × 1000 cm^3/dm^3 Volume of H_2 = 112 cm^3 3 done, 2 left today. You're making progress.