Nitrogen monoxide reacts with oxygen to form nitrogen dioxide. If this reaction is investigated in a closed system, a dynamic equilibrium is established. 2NO(g) + O2(g) ⇌ 2NO2(g)

1. (a)Explain why it is important to have a closed system to establish a dynamic equilibrium.[1]
2. (b)The pressure of the equilibrium mixture is decreased. The temperature of the equilibrium mixture is kept constant. Predict and explain what will happen, if anything, to the composition of the equilibrium mixture. prediction ................................................................................................................................... explanation ..................................................................................................................................[2]
3. (c)(i)The temperature of the equilibrium mixture is decreased. The pressure of the equilibrium mixture is kept constant. (i) Suggest why the position of equilibrium moves to the right.[1]
4. (c)(ii)Explain why the rate of reaction decreases.[2]
5. (d)Draw the ‘dot-and-cross’ diagram for a molecule of O2. Only include the outer shell electrons.[1]
6. (e)Nitrogen dioxide reacts with water to form nitric acid, HNO3, and nitrous acid, HNO2. Construct an equation for this reaction.[1]
7. (f)Nitric acid is a strong acid and nitrous acid is a weak acid. Describe the difference between a strong acid and a weak acid.[2]