Define rate of reaction - Leaving Cert Chemistry - Question 9 - 2015

The graph should have time (in minutes) on the x-axis and volume (in cm³) on the y-axis. Ensure the axes are correctly labeled and all points are accurately plotted, connecting them smoothly. The curve must start from (0, 0).

The rate of reaction decreases because, as the reactants (seashells and acid) are used up, their concentrations decrease. According to the collision theory, less concentration leads to fewer effective collisions between reactant particles, thereby slowing down the reaction rate.

The reaction is considered to have ended when the volume of gas collected in the gas syringe remains constant, meaning no more bubbles are produced, indicating that all seashells have reacted.

From the graph, locate the point corresponding to 3.5 minutes on the x-axis, and then find the corresponding volume on the y-axis. The volume of carbon dioxide produced after 3.5 minutes is approximately 52 cm³.

The average rate can be calculated using the formula:

$\text{Average Rate} = \frac{\text{Volume Produced}}{\text{Time}}$

Using the previously mentioned volume of 52 cm³ over 3.5 minutes, the calculation becomes:

$\text{Average Rate} = \frac{52 }{3.5} \approx 14.86 \text{ cm}^3 \text{ per minute}$

The rate of reaction would have increased (faster) because powdered seashells have a larger surface area, leading to more frequent collisions with the acid particles.

The rate of reaction would have increased (faster) due to a higher concentration of HCl, which results in more particles available to collide with the seashells.

The rate of reaction would have decreased (slower) because lowering the temperature reduces the kinetic energy of the molecules, leading to fewer effective collisions.