# Does Pressure affect rates of reaction?

Among the factors that affect rate of reaction, pressure is a major factor that do affect rates of reaction.

Yes, there has been a question whether pressure affects rates of reaction, but the truth is that Pressure is one of the factors that affect rates of reaction.

When pressure is increased, there is a decrease in the space available for gaseous reactants and thus making the gaseous particles to be very close to each other making them to collide often and thus increasing the frequency of collision (frequency of effective collisions) and thus increasing the rate of reaction.

I have to mention that pressure only affects the rate of reaction of gaseous reactants by decreasing the space available in the vessel for the reactants.

Pressure is a term used when you are referring to the concentration of gaseous reactants and I am going to discuss briefly how pressure affects the rate of reaction.

Pressure is one of the many factors that affect rate of reaction just like the way temperature affects rate of reaction. Pressure has a way it affects rate of reaction by decreasing the volume once you increase force on an area.

## Specific examples on how Pressure affects rates of reaction

Example 1

If nitrogen combined with oxygen in a 40cm3 vessel capacity at 200mmHg pressure. If pressure increase to 350mmHg. Explain what will happen to the rate of reaction and to the volume of the vessel.

Solution

Once the pressure is increased to 350mmHg, the volume of the container for the reaction mixture decreases thus making the gaseous particles to be very close and thus increasing the frequency of collisions.

Example 2

Example 1

Consider this reaction

N2 + H2 === 2NH3

If nitrogen combined with Hydrogen to form ammonia in a 100cm3 vessel capacity at 200mmHg pressure. I

Explain what happens to the reaction rate when pressure is decreased to 100mmHg.

Solution

When pressure is decreased then the volume of the vessel increased thus increasing the space available for the particles thus creating more space and decreasing the collisions of the reactant particles per unit time and consequently decreases the rate of reaction.

Example 3

Consider the reaction below

CH4 + O2==CO2 + H2O

If the reaction occurs in a 1 dm3 volume capacity at 600mmHg, what happens to the rate of reaction and collision theory rate if pressure doubles?

Solution

Pressure doubling means increase in pressure which will decrease the volume of the container or reaction vessel; and a s a result the space decreases because more force is applied on area reducing the available volume or space thus making same amount or number of gaseous reactant particles to be in the same space thereby being crowded in a smaller space increasing frequency of collisions and thus rate of reaction.

In conclusion, increase in pressure decreases the volume of the container making the same amount of gaseous particles to be closer to each other in a smaller space thereby increasing the frequency at which they collide with each other and thus increasing the frequency of collisions.