Measuring rates of reaction

Changes in Concentration

Definition:

• Measuring the rate of a chemical reaction involves observing how quickly reactants turn into products.

Importance:

• It helps us understand reaction speed.
• Crucial for controlling industrial processes and ensuring safety.

Changes in Concentration:

• One way to measure the rate is by monitoring changes in reactant concentration.

Example:

• Suppose we have a reaction where A turns into B.

• At the start, we have 1 $\frac{mol}{litre}$ of A and 0 $\frac{mol}{litre}$ of B.

• After 10 seconds, we measured 0.8 $\frac{mol}{litre}$ of A and 0.2 $\frac{mol}{litre}$ of B.

• The change in A's concentration is 1.0 $\frac{mol}{litre}$ - 0.8 $\frac{mol}{litre}$ = 0.2 $\frac{mol}{litre}$

• The change in B's concentration is 0.2 $\frac{mol}{litre}$ - 0 $\frac{mol}{litre}$ = 0.2 $\frac{mol}{litre}$

• The time taken is 10 seconds.

• Rate of reaction = $\frac{\text{Change in concentration of A}}{\text{Time}}$ = $\frac{0.2 \frac{mol}{litre}}{10 s}$ = 0.02 $\frac{mol}{litres}$

Units:

• The rate of reaction is measured in $\frac{mol}{litre}$ (mol/litre/s).
• It tells us how many moles of reactant disappear or moles of product appear per litre per second.