Chemistry 9701/33 March 2018 | Cambridge AS Level Past Papers With Mark Scheme

### 1. Investigating the Effect of Temperature on Reaction Rate:
- The reaction involves sodium thiosulfate (FA 1) reacting with a strong monoprotic acid (FA 2) to produce a sulfur precipitate.
- The experiment involves timing how long it takes for the sulfur precipitate to obscure a print as the reaction progresses, allowing you to measure the reaction rate at various temperatures.
- The method involves heating the solutions and mixing them while monitoring the time it takes for the precipitate to form. The temperature is adjusted, and the rate of reaction is calculated.

- Key aspects of the experiment:
- You calculate the rate of reaction using the formula:
\\[
\\text{Rate} = \\frac{1000}{\\text{Reaction Time}}
\\]
- You will also calculate the concentration of sodium thiosulfate and the strong monoprotic acid, HZ, in mol/dm³.
- You are expected to draw a graph of the rate of reaction versus temperature and analyze how temperature affects the rate.

### 2. Qualitative Analysis:
- This section involves testing unknown solutions (FA 3, FA 4, FA 5) for the presence of specific ions.
- Various reagents like sodium carbonate, sodium hydroxide, barium chloride, and potassium iodide are used to identify the ions in the unknown solutions.
- The experiment requires you to record observations such as color changes, precipitate formation, and gas evolution. You will also need to write down the ionic equations for the reactions that occur during testing.

- Tests include:
- Addition of reagents to form precipitates.
- Identification of gases produced.
- Reaction of certain ions with specific reagents to determine the identity of anions or cations.