Question

Consider the following system at equilibrium

N2(g)+3H2(g) <------> 2NH3(g)+ heat

Indicatre which way the reaction wil shift when making the following changes

1. Decreasing in the temperture

2. Increasing in the temperture

3. Removing some of NH3

4. Removing some of the H2O

5. Adding some O2

6. Removing some N2

****Pick from these answers ****

A. Forward reaction will increase

B. Reverse reaction will increase

C. There will be no change in either direction

Answer 1

This is a reversible reaction and governed by the Le Châtelier's principle where equilibrium tends to shift in the direction that opposes the change brought in the equilibrium system.  This reaction is exothermic and have only gaseous species in either side. So:

1. Decreasing in the temperture: A. Forward reaction will increase (to over come the heat loss)

2. Increasing in the temperture: B. Reverse reaction will increase (to consume the excess heat)

3. Removing some of NH3: A. Forward reaction will increase (to avoid the loss of NH3)

4. Removing some of the H2O: C. There will be no change in either direction (not present in equation)

5. Adding some O2: [introduction of inert gas at constant volume there is no effect on equilibrium state]: C. There will be no change in either direction

[But, introduction of inert gas (say O2 here) at constant pressure, backward reaction will favour]: B. Reverse reaction will increase

6. Removing some N2: B. Reverse reaction will increase (to get more N2, product will dissciate more)