2019 - Q15
What is the concentration of hydroxide ions (in mol L–1) in a solution that has a pH of 8.53?
A. 3.0 × 10^–9
B. 3.4 × 10^–6
C. 5.5
D. 3.0 × 10^5
2019 - Q28 (5 marks)
Assess the usefulness of the Brønsted–Lowry model in classifying acids and bases. Support your answer with at least TWO chemical equations.
2019 - Q33 (4 marks)
A student adds 1.17 g of Al(OH)3(s) to 0.500 L of 0.100 mol L–1 HCl(aq).
Calculate the pH of the resulting solution. Assume that the volume of the resulting solution is 0.500 L.
2019 - Q18
Consider the following equilibrium.
Which row of the table correctly identifies the strongest acid and the strongest base in this system?
2020 - Q33 (6 marks)
Excess solid calcium hydroxide is added to a beaker containing 0.100 L of 2.00 mol L−1 hydrochloric acid and the mixture is allowed to come to equilibrium.
(a) Show that the amount (in mol) of calcium hydroxide that reacts with the hydrochloric acid is 0.100 mol. (2 marks)
(b) It is valid in this instance to make the simplifying assumption that the amount of calcium ions present at equilibrium is equal to the amount generated in the reaction in part (a).
Calculate the pH of the resulting solution. (4 marks)
2021 - Q23 (4 marks)
Methanoic acid reacts with aqueous potassium hydroxide. A salt is produced in this reaction.
(a) Write a balanced chemical equation for this reaction. (2 marks)
(b) Is the salt acidic, basic or neutral? Justify your answer. (2 marks)
2020 - Q18
An aqueous solution of sodium hydrogen carbonate has a pH greater than 7.
Which statement best explains this observation?
2020 - Q18
An aqueous solution of sodium hydrogen carbonate has a pH greater than 7.
Which statement best explains this observation?
2021 - Q34 (5 marks)
Gaseous HCl was bubbled into water and two solutions, X and Y. Solutions X and Y contain the same type of ions. The pH of each was monitored over time and recorded in the graph shown.
Explain the observed pH of the water and each of the solutions at t0, t1 and t2. Include a relevant balanced chemical equation in your answer.
2021 - Q15
What is the pH of the resultant solution after 20.0 mL of 0.20 mol L−1 HCl(aq) is mixed with 20.0 mL of 0.50 mol L−1 NaOH(aq)?
A. 11.8
B. 13.2
C. 13.5
D. 14.0
2022 - Q22 (2 marks)
The following equation describes an equilibrium reaction.
2022 - Q10
Which equation shows the hydrogen carbonate ion acting as a Brønsted−Lowry acid?
2022 - Q25 (3 marks)
The pH of two aqueous solutions was compared.
Explain why the HCN(aq) solution has a higher pH than the HCl(aq) solution. Include a relevant chemical equation for the HCN(aq) solution.
2022 - Q34 (4 marks)
Sodium hypochlorite (NaOCl) is the active ingredient in pool chlorine. It completely dissolves in water to produce the hypochlorite ion (OCl−), which undergoes hydrolysis according to the following equilibrium.
OCl−(aq) + H2O(l ) <--> HOCl(aq) + OH−(aq)
The equilibrium constant for this reaction at 25°C is 3.33 × 10^−7. For pool chlorine to be effective the pH is maintained by a different buffer at 7.5 and the hypochlorous acid (HOCl) concentration should be 1.3 × 10^−4 mol L−1.
Calculate the volume of 2.0 mol L−1 sodium hypochlorite solution that needs to be added to a 1.00 × 10^4 L pool to meet the required conditions.