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Describe the effect on the value of Keq by the following changes

N2+3H2= 2NH3 change in heat= -92KJ

a) increase N2

b) increase temperature

c) increase volume

d) add a catalyst

Louis-Philippe B

Thank you for your question!

Some of these phenomena will change the equilibrium constant, others not.

Situation a) will not change the equilibrium constant. Indeed, according to the Le Châtelier principle, the system will always return to its original equilibrium state, assuming no other changes in conditions.

Situation b) will change the equilibrium constant by favouring the endothermic reaction. In this case, the inverse reaction is endothermic, so there will be more reactants. (I will let you figure out what the presence of more reactants means for Ke!)

Situation c) could change the equilibrium constant, but there is no information on the state of matter of each substance in the reaction. I would recommend that you check the reaction to make sure that the state of matter of each substance isn't written. If some or all of the substances of the reaction are gaseous, the side of the equation with more moles of gas could be favoured because an increase in volume increases the amount of space for more moles of gas.

Situation d) would not change the equilibrium constant. Indeed, a catalyst increases the efficiency of the forward and inverse reactions simultaneously, therefore generating no change in the net amount of products and reactants.

This webpage of the Alloprof website (in French) explains the equilibrium constant :

https://www.alloprof.qc.ca/fr/eleves/bv/chimie/la-constante-d-equilibre-c1043

Don't hesitate if you need more help!