Question

For the following equilibrium reaction: CO + 3H2 <---> CH4 +H2O + HEAT

a) Describe what will happen to the concentration of CO when you cool this reaction?

b) Describe what will happen to the CH4 concentration when you add hydrogen gas to the reaction?

c) Draw the energy diagram for this reaction. Be sure to show the relative total energy of the reactants and of the products. Also, identify the activation energy for this reaction on your energy diagram.

Answer 1

This question is based on Le-Chatleir's Principle. This principle states that if a rxn is in dynamic equilibrium and if the equilibrium is disturbed by changing some conditions, then the equilibrium will shft to counteract the change.

Let's look at our problem:

CO + 3H2 <---> CH4 +H2O + HEAT

a) In this part we are disturbing the equilibrium by cooling the rxn. So according to Le-Chatleir's Principle, the equilibrium will shift in a direction that will cancer out this change. As forward direction is producing heat so if we cool the rxn the equilibrium will shift in forward direction (that is toward products) to cancel out the change. This will result in increase in formation of products and hence decrease in concentration of CO.

b) Now, if we increase H₂ concentration by adding more of it, the equilibrium will shift forward so that the additional H₂ is consumed and the equilibrium is restored. This will result in more product formation and hence concentration of CH4 will increase.

c) Energy diagram is a plot of potential energy of reactants and products. On left we have energy of reactant and it can be denoted by E_R . It is the total energy that reactant has whereas on right side we have total energy of products (E_P ). As heat is being released it means total energy of system is decreasing this is why E_R > E_P .

To convert to product the reactants need to attain a certain amount of extra energy called as activation energy (E_a ). The activation energy barrier has bee shown by a hill in the curve. The reactants must "cross this hill" that is gain this energy to convert into products.

Hope this helps! Kindly upvote :)