What effect will increased pressure have on 4A (g) + 5B (g) ---> 2C (g) + 7D (g)

a- no change

b- everything will increase

c- C and D will increase

d- A and B will increase

Explanation:

The question makes sense only if the equation is an equilibrium reaction:

This is, A and B react to produce C and D, forward reaction; and C and D react to form A and B, reverse reaction.

Then, you can study the effect of increased pressure using LeChatelier's principle.

To counteract the disturbing effect produced by increased pressure on the equilibrium, the system will react shifting the toward to the side where the pressure could be decreased.

That would be toward the side that has less gas molecules.

Since both sides have 9 molecules (4 + 5 = 2 + 7 = 9), the equilibrium concetrations will not change.

That is represented by the first choice: no change.