A student used the apparatus in Figure 7 to investigate the rate of the reaction between a metal and dilute hydrochloric acid - Edexcel - GCSE Chemistry Combined Science - Question 5 - 2022 - Paper 1

To calculate the mean rate of production, we first find the volume of hydrogen produced in the first 90 seconds. From the graph, the volume at 90 seconds is read as 29 cm³.

Rate Calculation:

$ext{Rate} = \frac{\text{Volume of gas}}{\text{Time in seconds}}$

Thus,

$ext{Rate} = \frac{29 \text{ cm}^3}{90 \text{ seconds}} = 0.3222 \text{ cm}^3 \text{ per second}$

The measurements could have been stopped at 9 minutes because the volume of gas would have reached a plateau, indicating that the reaction had completed and no further gas was being produced.

The rate of reaction increases with higher acid concentration because there are more acid particles present in the solution. This leads to a greater frequency of collisions between the acid particles and the metal, resulting in an increased number of successful reactions per unit of time.

The correct option is A: use the same acid but at a lower temperature. Lowering the temperature generally decreases the kinetic energy of particles, which would slow down the reaction, not increase it. The other options either do not pertain to increasing the rate effectively or are incorrect.

The student can make smaller marble chips by:

1. Crushing the large chips: Use a mortar and pestle to break down the large chips into smaller pieces.

2. Sifting: Use a sieve to separate the crushed chips into different sizes, thus sorting them into small and medium sizes.