Chemistry 9701/51 Oct Nov 2021 | Cambridge AS Level Past Papers With Mark Scheme

1. Determining enthalpy changes in reactions involving potassium hydrogencarbonate (KHCO3) and potassium carbonate (K2CO3), including reasons why ∆Hr cannot be measured directly for the decomposition of KHCO3.
2. Calculation of masses of KHCO3 and K2CO3, percentage error in mass measurement, and enthalpy changes using energy formulas.
3. Using Hess's law to calculate the enthalpy change (∆Hr) for the decomposition reaction of KHCO3.
4. Discussion on experimental discrepancies, safety precautions, and suggestions for improving accuracy in determining enthalpy changes.
5. Investigation of reaction rates between calcium carbonate and hydrochloric acid, including graphing data, calculating half-lives, and determining the rate constant (k).
6. Analysis of the effect of temperature on the rate constant (k) and considerations for improving the reliability of results in experiments involving calcium carbonate in antacid tablets.