Altering the pressure in a reversible chemical reaction affects the equilibrium position according to Le Chatelier's principle, which states that if a system at equilibrium is subjected to a change in pressure, temperature, or concentration of reactants or products, the system will adjust its equilibrium position to counteract the change.In the case of pressure changes, the reaction will shift in the direction that helps to minimize the pressure change. This means that if the pressure is increased, the reaction will shift towards the side with fewer moles of gas, as this will help to reduce the pressure. Conversely, if the pressure is decreased, the reaction will shift towards the side with more moles of gas, as this will help to increase the pressure.The factors that determine whether the reaction will shift to the side with a greater or lesser number of moles of gas are the stoichiometry of the reaction the balanced chemical equation and the initial pressure change increase or decrease .For example, consider the following gaseous reaction:N2 g + 3H2 g 2NH3 g In this reaction, there are 4 moles of gas on the reactant side 1 mole of N2 and 3 moles of H2 and 2 moles of gas on the product side 2 moles of NH3 . If the pressure of the system is increased, the reaction will shift towards the side with fewer moles of gas, which is the product side formation of NH3 . This will help to reduce the pressure by decreasing the total number of gas particles in the system.On the other hand, if the pressure of the system is decreased, the reaction will shift towards the side with more moles of gas, which is the reactant side formation of N2 and H2 . This will help to increase the pressure by increasing the total number of gas particles in the system.In summary, altering the pressure in a reversible chemical reaction affects the equilibrium position by shifting the reaction towards the side with either more or fewer moles of gas, depending on whether the pressure is decreased or increased, respectively. The stoichiometry of the reaction and the initial pressure change are the main factors that determine the direction of the shift.