The reaction between hydrogen gas H2 and iodine gas I2 to form hydrogen iodide HI can be represented by the following balanced equation:H2 g + I2 g 2HI g This reaction is an example of a homogeneous gas-phase reaction, which means that all reactants and products are in the gas phase. The rate of this reaction can be affected by various factors, including pressure.According to Le Chatelier's principle, if a system at equilibrium is subjected to a change in pressure, the system will adjust itself to counteract the change and re-establish equilibrium. In the case of this reaction, an increase in pressure will favor the side of the reaction with fewer moles of gas, while a decrease in pressure will favor the side with more moles of gas.In this reaction, there are 1 mole of H2 and 1 mole of I2 on the reactant side, and 2 moles of HI on the product side. Therefore, when the pressure is increased, the reaction will shift towards the side with fewer moles of gas, which is the reactant side H2 and I2 . This means that the rate of the forward reaction formation of HI will decrease, and the rate of the reverse reaction decomposition of HI will increase.Conversely, when the pressure is decreased, the reaction will shift towards the side with more moles of gas, which is the product side HI . This means that the rate of the forward reaction formation of HI will increase, and the rate of the reverse reaction decomposition of HI will decrease.In summary, increasing the pressure will decrease the rate of the reaction between hydrogen gas and iodine gas to form hydrogen iodide, while decreasing the pressure will increase the rate of the reaction.