5.1.2 - How far?

Question 1

Predict, with a reason, whether the forward reaction is exothermic or endothermic.
Temperature / K Kp / atm−1
- 298 K - Kp = 2.19 × 10^12
- 1000 K - Kp = 2.03 × 10^−1

Answer 1

• Exothermic
• Kp decreases as temperature increases

Question 2

2NO(g) + O2(g) ⇌ 2NO2(g)
The chemist increases the pressure of the equilibrium mixture at the same temperature. State, and explain in terms of Kp, how you would expect the equilibrium position to change. (3)

Answer 2

Equilibrium shift:
- (Equilibrium position) shifts to right / forward / towards products

Effect of increased pressure on Kp expression:
- Ratio (in Kp expression) decreases
- Denominator/bottom of Kp expression increases more
(than numerator/top)

Equilibrium shift (Kp expression);
- Ratio (in Kp expression) increases to restore Kp
- Numerator/top of Kp expression increases to restore Kp

Question 3

What is a heterogeneous equilibrium? (1)

Answer 3

• (Species have) different states / phases