Question

(AP CHEMISTRY) Please help me answer these questions, I would appreciate it:

1. Given the reaction: 2 NOF(g) ⇌ 2 NO(g) + F2(g) at a certain temperature the value for KP is 1200.

What will happen to the value for Q if the volume was doubled?

Which way will the reaction shift to reach equilibrium? If it were to increase/decrease, by how much?


2. The reaction: 2NO2(g) ⇌ N2O4(g) is an exothermic reaction, ΔH=-58. 0 kJ/molrxn at 0°C the KP is 58.

a) Use an ICE table to find the equilibrium pressures.


3. Consider the reaction A(g) ⇌ 2B(g) + C(g), K = 2. 12 x 10-2. The reaction is at equilibrium at in a 1. 00 L container. The reaction is then placed into a container that has half the volume. How will Q relate to K? Which direction will the reaction proceed to reach equilibrium? If K is greater/ lesser, by how much is it so?

Answer 1

Doubling the volume will cause Q to decrease, since the concentration of all the gases in the reaction will decrease. The reaction will shift towards the side with more moles of gas to re-establish equilibrium, which in this case is towards the reactant side (left). The new equilibrium concentration can be calculated using the expression Q = (NO)^2 * F2 / (NOF)^2 * 2 and the given KP value of 1200.
The ICE table for the given reaction is:
2NO2(g) ⇌ N2O4(g)
Initial P 0
Change -2x +x
Equil. P-2x x
Since KP = P(N2O4) / P^2(NO2), substituting the equilibrium concentrations into the expression and solving for x gives:

KP = (x)^2 / (P - 2x)^2 = 58
x = 0.272 atm

Therefore, the equilibrium concentrations are P(NO2) = P - 2x = P - 0.544 atm and P(N2O4) = x = 0.272 atm.

If the volume is halved, the pressure will increase since the same number of moles of gas are now in half the volume. Q will initially be greater than K, since the concentration of A will be greater than that of B and C. The reaction will shift towards the product side to re-establish equilibrium, which in this case is towards the right. Since K is a constant at a given temperature, it will remain the same. However, the numerical value of Q will change and eventually reach the value of K once equilibrium is reached. The new equilibrium concentration can be calculated using the expression Q = (B)^2 * C / (A)^1 * 2 and the given K value of 2.12 x 10^-2.