Answer:
ExplanaA) A decrease in reactant concentration reduces the frequency of successful collisions. tion:
As a reactant gets used up, there are fewer molecules present to collide with others. A reaction depends on molecular collisions. When there are fewer collisions, the reaction slows down.
B) is wrong. A reaction is usually carried out at constant temperature,
C) is wrong. Not all reactions need catalysts.
D) is wrong. If the temperature is constant, pressure will have little effect on the movement and energy of molecule.
