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Chemical Reactivity · Part 3 of 3
12 exam-style questions with model answers, plus 16 quick multi-choice questions — every question on this part of the standard, grouped by the 4 pages of notes they come from.
Write a full answer before you reveal the model one. That comparison is where the learning happens.
Define an acid and a base in terms of proton transfer, and give the conjugate base of HNO3.
For HCl + H2O → Cl− + H3O+, identify the acid and base and explain your reasoning.
Water reacts with HCl to give Cl− and H3O+, but with NH3 to give NH4+ and OH−. Explain how water can behave as both an acid and a base, identify the conjugate pairs in each reaction, and explain what this implies about how acid and base strength should be described.
Explain the difference between a strong acid and a weak acid, and write an equation for each.
Explain why 'strong' and 'concentrated' do not mean the same thing, using examples.
Equal volumes of 0.10 mol L−1 hydrochloric acid and 0.10 mol L−1 ethanoic acid are each reacted with excess magnesium ribbon. Predict and explain the difference in the initial rate of reaction and in the total volume of hydrogen produced, and explain why these two answers are not the same kind of comparison.
State which of a strong or a weak acid of the same concentration has the lower pH, and why.
Explain why a 0.1 mol L−1 solution of hydrochloric acid conducts electricity better than a 0.1 mol L−1 solution of ethanoic acid.
A student measures the pH of two acids and finds solution A (0.010 mol L−1) has pH 2.0 and solution B (0.10 mol L−1) has pH 2.9. The student concludes that A is the stronger acid. Evaluate this reasoning, and describe what further evidence would confirm the conclusion.
Calculate the pH of a 0.010 mol L−1 solution of hydrochloric acid.
Calculate the pH of a 0.020 mol L−1 solution of sodium hydroxide, showing all steps.
Calculate the pH of 0.0050 mol L−1 sulfuric acid (H2SO4, assume both protons are fully donated). Then explain why the pH of a 0.10 mol L−1 solution of ethanoic acid cannot be calculated using the same method, and state what additional information would be needed.