Question

in an experiment, a student wants to increase the rate of a reaction that involves gases. which change to the reactants would accomplish this?
increase the volume to decrease pressure and to increase concentration.
increase the volume to increase pressure and to decrease concentration.
decrease the volume to decrease pressure and to increase concentration.
decrease the volume to increase pressure and to increase concentration.

Explanation:

The rate of a gas - phase reaction increases with an increase in the concentration of reactants. According to Boyle's law ($P_1V_1 = P_2V_2$), decreasing the volume of a gas increases its pressure and concentration. Higher concentration leads to more frequent collisions between reactant molecules, thus increasing the reaction rate.

Answer:

Decrease the volume to increase pressure and to increase concentration.