P- Equilibria =)

Question 1

Explain how the addition of a catalyst changes the activation energy. (2)

Answer 1

• alternative route
• w/ a ↓ Ea (∴ ↑ molecules can react)

Question 2

Explain the meaning of the term dynamic equilibrium. (2)

Answer 2

• rate of forward reaction = rate of reverse reaction
• conc. of reactants + products remain constant

Question 3

Suggest two reasons why the operation of this process at a pressure much higher than 5 MPa would be very expensive. (2)

Answer 3

1. energy required to provide high pressure
2. strong pressure vessels needed- withstand high pressure

Question 4

CH4 (g) + 2H2O (g) ⇌ CO2 (g) + 4H2 (g)
The mixture was placed in a flask of volume greater than 5.0dm3 and allowed to reach equilibrium at the same temperature.
State and explain the effect on the amount of hydrogen. (3)

Answer 4

↑
- ↓ pressure
- eq. shifts to RHS w/ ↑ moles

Question 5

State the Le Chatelier’s principle. (1)

Answer 5

Position of equilibrium moves to OPPOSE any change.

made it up from memory- better check.

Question 6

Explain how the use of a catalyst affect the cost of a reaction. (2)

Answer 6

• allows a lower temp to be used
• ↓ cost

Question 7

State and explain the effect of using a catalyst on the yield of methanol in this equilibrium. (2)

Answer 7

• x effect
• ↑ rate of forward + reverse reactions equally

Question 8

2A + B ⇌ 3C + D
Justify the statement that adding more water to the equilibrium mixture will lower the amount of A in the mixture. (3)

Answer 8

• conc (of all) ↓
• eq. shifts to the sides w/ ↑ moles
• to oppose ↓ in conc

x dilution

Question 9

Define the term catalyst. (2)

Answer 9

• speeds up a chemical reaction
• remains unchanged

Question 10

At high temperatures, nitrogen is oxidised by oxygen to form nitrogen monoxide in a reversible reaction as shown in the equation below.
N2(g) + O2(g) ⇌ 2NO(g)
State and explain the effect of an increase in pressure on the yield of nitrogen monoxide in the above equilibrium. (3)

Answer 10

• no effect
• same no. of gaseous moles on either side
• both sides affected equally

Question 11

An equation for this formation of methanol is given below.
CO2(g) + 3H2(g) CH3OH(g) + H2O(g)
Suggest one environmental advantage of manufacturing methanol fuel by this reaction. (1)

Answer 11

CO2 produced when burning is used up