The effect of increasing pressure on the reaction rate between hydrogen gas H2 and iodine gas I2 to form hydrogen iodide 2HI can be explained using the collision theory of chemical reactions. The collision theory states that for a reaction to occur, the reactant particles must collide with each other with sufficient energy and proper orientation.The reaction between hydrogen gas and iodine gas is a bimolecular reaction, which means that two molecules are involved in the rate-determining step. The balanced equation for this reaction is:H2 g + I2 g 2HI g When the pressure is increased, the concentration of the reactants H2 and I2 in the reaction mixture also increases. This is because the volume of the system decreases, causing the gas molecules to be closer together. As a result, the frequency of collisions between the reactant molecules increases, leading to a higher reaction rate.According to the collision theory, an increase in the number of collisions between the reactant molecules will increase the probability of successful collisions collisions with sufficient energy and proper orientation , thus increasing the reaction rate.In summary, increasing the pressure in the reaction between hydrogen gas and iodine gas to form hydrogen iodide will increase the reaction rate due to the increased frequency of collisions between the reactant molecules, as explained by the collision theory of chemical reactions.