The rate of reaction between magnesium ribbon and dilute hydrochloric acid at room temperature is investigated - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2018 - Paper 1

To calculate the rate of reaction at the tangent, determine the gradient of the tangent line drawn on the graph at the specified point. The rate of reaction is calculated as:

$\text{Rate of reaction} = \frac{\text{Change in Volume of Gas}}{\text{Change in Time}}$

The expected line would demonstrate a steeper increase than that of the magnesium ribbon, indicating a faster rate of reaction due to the greater surface area of the powdered magnesium.

To find the number of moles:

$\text{Number of moles} = \frac{\text{mass}}{\text{molar mass}}$

Using the given data:

$\text{Number of moles} = \frac{0.1 \text{ g}}{24 \text{ g/mol}} = 0.00417 \text{ mol}$

The balanced chemical equation is:

$\text{Mg} + 2\text{HCl} → \text{MgCl}_2 + \text{H}_2$

From the reaction, one mole of magnesium reacts with two moles of HCl. Since we have 0.5 mol of HCl, it will require:

$0.5 \text{ mol HCl} \times \frac{1 \text{ mol Mg}}{2 \text{ mol HCl}} = 0.25 \text{ mol Mg}$

Since we only have 0.5 mol of Mg available, magnesium is indeed in excess.

As temperature increases, the kinetic energy of the particles increases. This results in more frequent and effective collisions between the reactant particles, leading to an increased rate of reaction.

Increasing the concentration of A increases the number of particles in a given volume. This leads to a higher likelihood of collisions between the reactant particles, therefore increasing the rate of reaction.