Effect of concentration and pressure on rate
The rate of a chemical reaction can be changed by altering the concentration of a reactant in solution, or the Force exerted over an area. The greater the pressure, the greater the force exerted over the same area. of a gaseous reactant.
If the concentration or pressure is increased:
- there are more reactant particles per unit volume (ie the reactant particles become more crowded)
- there is a greater chance of the particles colliding, which leads to more successful collisions per second
- the rate of reaction increases
Compared to a reaction with a reactant at a low concentration (if a solution) or a low pressure (if a gas), the graph line for the same reaction but at a higher concentration or pressure:
- has a steeper In a graph, the gradient is the steepness of the line. The greater the gradient, the greater the rate of change. at the start
- becomes horizontal sooner
This shows that the rate of reaction was greater at the higher concentration or pressure.