Consider the following reaction in a closed system:
h2(g) + i2(g) → 2hi(g). which of the following will decrease the rate of the forward reaction?

a.) add some h2
b.) remove some hi
c.) increase the volume
d.) increase the temperature

C. Increasing the volume of gas particles of H2 and I2 will decrease the rate of the forward reaction. As the gas particles will not undergo frequent collisions as much and thus will not produce as much product.

According to the Le Chatelier's principle, the reaction would shift to a direction where it can be in equilibrium. From the given choices, the forward reaction may be decreased by increasing the volume of the vessel to which these components are allowed to react. 

Atom is the smallest particle of pure sustance which can take part in a chemical reaction.A chrged atom is called an ion.

A molecule of an element or compound is the smallest particle of it that is stable and capable of independent existence. The molecules of element and compound are different.