⚡ Show all working — the AI marks against the AQA mark scheme. Method marks awarded for correct working even if the final answer is wrong.
4 marksGas syringe methodAQA 8462 P2 style
A student investigates the effect of concentration of hydrochloric acid on the rate of reaction with marble chips (CaCO₃). Describe the method and explain how the student would use the results to compare rates at different concentrations. (4 marks)
Hint: Method: marble chips + HCl → CO₂. Measure: gas volume over time. Control variables. Compare: initial gradient = rate.
+40 XP
1 markCross methodAQA 8462 style
In the sodium thiosulfate and HCl experiment, the rate is measured by timing until the cross disappears. How is rate calculated from this timing?
A Rate = time taken
B Rate = 1 ÷ time
C Rate = mass ÷ time
D Rate = time²
3 marksInterpret graphAQA 8462 style
Two experiments produce the same total volume of CO₂. Experiment A uses 1 mol/dm³ HCl; Experiment B uses 2 mol/dm³ HCl, same mass of CaCO₃. Sketch-describe the graph and explain the differences. (3 marks)
Hint: Same total product (same CaCO₃). Different rates (different HCl concentration). Steeper = faster rate. Same endpoint.