The effect of pressure on the rate of the reaction between hydrogen gas H2 and iodine gas I2 can be explained using the collision theory. The reaction between hydrogen and iodine gas is as follows:H2 g + I2 g -> 2HI g According to the collision theory, the rate of a reaction depends on the frequency of effective collisions between reactant molecules. An increase in pressure results in an increase in the concentration of the reactants, which in turn increases the number of collisions between the reactant molecules.In the case of the reaction between hydrogen gas and iodine gas, increasing the pressure will increase the concentration of both H2 and I2 molecules in the reaction vessel. This leads to a higher frequency of collisions between H2 and I2 molecules, resulting in a higher rate of reaction.In summary, increasing the pressure of the reaction between hydrogen gas and iodine gas will increase the rate of the reaction, as explained by the collision theory.