Question

1) For the following reaction at equilibrium in a reaction vessel, which one of these changes would cause the Br2 concentration to decrease?


2NOBr(g)  2NO(g) + Br2(g), ∆Horxn= 30 kJ/mol

A) Increase the temperature.

B) Remove some NO.

C) Add more NOBr.

D) Compress the gas mixture into a smaller volume.

Answer 1

A)
Forward reaction is endothermic in nature
we are increasing temperature or adding heat here
so, according to Le Chatelier's principle,
equilibrium will move in direction which absorbs heat
hence, forward reaction will be favoured
Equilibrium moves to product side
Br2 concentration will increase

B)
we are removing a product
According to Le Chatelier's Principle,
Removing product will shift reaction towards product side
Equilibrium moves to product side
Br2 concentration will increase

c)
we are adding a reactant
According to Le Chatelier's Principle,
Adding reactant will shift reaction towards product side
Equilibrium moves to product side
Br2 concentration will increase

D)
We are decreasing volume here
In other words we are trying to increase pressure
so, according to Le Chatelier's principle,
Reaction will try to decrease the pressure
Hence it will move in a direction which have lesser gaseous molecules
Here reactant has less gaseous molecule
So equilibrium will move to left
Answer: Equilibrium moves to reactant side
Br2 concentration will decrease

Answer: D