Question

in a reaction where hydrogen gas (H2) and hydrogen iodide (HI) are colorless, but iodine gas (I2) is deep purple, what will happen if some hydrogen gas is removed
a) the system will shift to the right, becoming less purple as more I2 is formed
b) the system will shift to the left, becoming less purple as more H2 and HI are formed
c) the system will remain unchanged, as H2 is not part of the equilibrium
d) the reaction will stop until more H2 is added

Answer 1

In a chemical equilibrium, when a change is made to a system (such as removing a reactant), the system will respond by shifting the equilibrium position to counter that change, according to Le Chatelier's principle.

In the reaction involving hydrogen gas (H₂) and hydrogen iodide (HI) forming iodine gas (I₂), if some hydrogen gas (H₂) is removed, the equilibrium will shift to the left to produce more H₂ and HI in order to compensate for the loss of H₂. As a result, this means that less I₂ will be formed, leading to a decrease in the concentration of the deep purple iodine gas, making the system less purple.

Therefore, the correct answer is:

**b) the system will shift to the left, becoming less purple as more H2 and HI are formed.**