Question

An increase in pressure in the reaction $2HI\left(g\right)\rightleftharpoons H_2\left(g\right)+I_2\left(g\right)$ would :

• A. produce more $I^{-}\left(aq\right)$
• B. produce more $H_2$
• C. not effect the system
• D. drive it to the right

Answer 1

The correct option is C not effect the system

According to Le Châtelier, if the pressure is increased, the position of equilibrium will move so that the pressure is reduced again. The pressure is caused by gas molecules hitting the sides of their container. The more molecules in the container, the higher the pressure will be. The system can reduce the pressure by reacting in such a way as to produce fewer molecules.

In this case, there are two moles on the left-hand side of the equation, and two on the right so the number of moles is same on both sides, hence, change in pressure does not effect equilibrium.