Draw a reaction profile (diagram of energy vs reaction coordinate) for a hypothetical reaction AB +C <=> A+BC in which the foward reaction has an activation energy of 100kJ mol-1 and the backward reaction has an activation energy of 75kJ mol-1. (ii). a catalyst introduces an extra step into the reaction and reduces Ea for the 1st step to 50kJ mol-1. Indicate the effect of the catalyst on the diagram. (iii). how would you expect the equilibrium constant for this reaction to vary with temperature?

We can't draw diagrams on this board.

Im not quite sure what type of diagram this is, could u like describe an example of what to do?

To draw a reaction profile for the given reaction AB + C ⇌ A + BC, we need to plot the energy of the system against the reaction coordinate (progress of the reaction).

(i) Without a catalyst:

Let's assume that the reactants AB and C have a higher energy than the products A and BC. The forward reaction (AB + C → A + BC) has an activation energy of 100 kJ mol-1, while the backward reaction (A + BC → AB + C) has an activation energy of 75 kJ mol-1.

On the y-axis, we will plot the energy of the system, and on the x-axis, we will plot the reaction coordinate (progress of the reaction). The diagram will have two peaks to represent the activation energies.

Starting from the reactants, the energy level will decrease as the reaction proceeds forward. At the transition state, there will be a peak representing the activation energy of 100 kJ mol-1. Then, the energy level will decrease again as the reaction continues forward. At the products, there will be a valley.

Returning to the reactants from the products, the energy level will increase as the reaction proceeds backward. At the second transition state, there will be another peak representing the activation energy of 75 kJ mol-1. Then, the energy level will decrease again as the reaction continues backward.

So, on the reaction profile diagram without a catalyst, there will be two peaks corresponding to the activation energies of the forward and backward reactions.

(ii) With a catalyst:

When a catalyst is introduced, it reduces the activation energy for the first step to 50 kJ mol-1. This means that the catalyst provides an alternative reaction pathway with a lower energy barrier.

On the reaction profile diagram, the effect of the catalyst can be represented by adding an additional lower-energy pathway for the firststep of the reaction. This alternative pathway will have a peak representing the reduced activation energy of 50 kJ mol-1.

So, with the catalyst, we will see two separate pathways on the reaction profile diagram, one with higher activation energy (75 kJ mol-1) for the backward reaction, and another with lower activation energy (50 kJ mol-1) for the forward reaction.

(iii) Effect of temperature on the equilibrium constant (K):

The equilibrium constant for a reaction, denoted as K, depends on the difference in energies between the reactants and products. As the temperature increases, the equilibrium constant can be expected to change.

In a general sense, an increase in temperature favors an endothermic reaction (where heat is absorbed) by shifting the equilibrium towards the products. This can be understood by Le Chatelier's principle, which states that a system at equilibrium will shift in the direction that relieves the applied stress.

For the given reaction AB + C ⇌ A + BC, if the forward reaction (AB + C → A + BC) is endothermic, an increase in temperature will shift the equilibrium towards the products (A + BC). Consequently, the equilibrium constant K will increase.

Conversely, if the forward reaction is exothermic (releases heat), an increase in temperature will shift the equilibrium towards the reactants (AB + C). In this case, the equilibrium constant K will decrease.

Therefore, the effect of temperature on the equilibrium constant depends on the thermodynamics of the reaction and whether it is exothermic or endothermic.