PCl5 <-> PCl3 + Cl2 PCl5 decomposes into PCl3 and Cl2 according to the equation above. A pure sample of Pcl5 is placed in a rigid, evacuated 1.00 L container. The initial pressure of the PCl5 is 1.00 atm. The temperature is held constant until the PCl5 reaches equilibrium with its decomposition products. The figures below shows the initial and equilibrium conditions of the system.

As the reaction progresses toward equilibrium, the rate of the forward reaction
A) increases until it becomes the same as the reverse reaction rate at equilibrium
B) stays constant before and after equilibrium is reached
C) decreases to become a constant nonzero rate at equilibrium
D) decreases to become zero at equilibrium

PCl5 <-> PCl3 + Cl2

PCl5 decomposes into PCl3 and Cl2 according to the equation above. A pure sample of Pcl5 is placed in a rigid, evacuated 1.00 L container. The initial pressure of the PCl5 is 1.00 atm. The temperature is held constant until the PCl5 reaches equilibrium with its decomposition products. The figures below show the initial and equilibrium conditions of the system.

As the reaction progresses toward equilibrium, the rate of the forward reaction

A) increases until it becomes the same as the reverse reaction rate at equilibrium

B) stays constant before and after equilibrium is reached

C) decreases to become a constant nonzero rate at equilibrium

D) decreases to become zero at equilibrium

Explanation:

At equilibrium, both forward and backward reactions take place with constant speed.

The reaction will never cease.

Due to this reason chemical equilibrium is called dynamic in nature.

At equilibrium:

the rate of forward reaction = rate of backward reaction

As the reaction progresses toward equilibrium, the rate of the forward reaction decreases to become a constant nonzero rate at equilibrium.

Answer is option C).