HSC Chemistry free practice questions with answers
Read question 1 and its full worked answer from paper 1 of our 20-paper HSC Chemistry set, then download the 4-page PDF. These are original practice questions, not official past papers. Page updated 3 November 2026.
The Ksp of BaSO₄ is 1.1 × 10−¹⁰ at 25 °C. Solid BaSO₄ is added to a 0.010 mol L−¹ solution of sodium sulfate. How many times less soluble is the salt in this solution than in pure water?
A 953
B 1.15 × 10−¹³
C 9530
D 1.05 × 10−³
[Equilibrium: solubility and Ksp]
Correct answer: A — 953
- Solubility in pure water = √Ksp = 1.05 × 10−⁵ mol L−¹.
- Ratio = 1.05 × 10−⁵ ÷ 1.10 × 10−⁸ = 953
- Why the other options are wrong:
- B (1.15 × 10−¹³): multiplied the solubilities
- C (9530): a power-of-ten slip
- D (1.05 × 10−³): inverted the ratio
Common-ion effect: adding an ion already in the equilibrium reduces solubility; with a fixed common-ion concentration, solubility = Ksp ÷ [common ion] (for a 1:1 salt).
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Questions about this sample
What is in the HSC Chemistry free sample?
The first 3 questions from paper 1 of the set, in the real exam layout, followed by the step-by-step worked answers. It is a 4-page PDF; this page shows question 1 with its answer.
How many full HSC Chemistry papers are there?
20 original papers for Year 12 students preparing for the NSW HSC. Each is a full practice examination with Section I 20 multiple-choice, Section II 80 marks, 100 marks in all, 3 hours working time plus 10 minutes reading time, with a worked solution for every question. Papers start at A$15.99 and download instantly as a PDF.
Are these official past papers?
No. The sample is taken from our own original practice paper and is not an official past paper or affiliated with any exam authority.