Rate of reacton/equilibrium

Question 1

Rate of reaction decreases over time.
Explain why, in terms of collision theory.

Answer 1

fewer collisions/ less frequent collisions

Question 2

Explain how a catalyst increases the rate of reaction.

Answer 2

-Catalyst lowers the activation energy (by providing an alternative route)
-A greater proportion of molecules have more energy greater than/equal to
activation energy ✓

Question 3

This question is about ammonia, NH3.

In industry, ammonia is made from nitrogen and hydrogen. This is a reversible reaction, as shown
in equilibrium 24.1 below.

N2(g) + 3H2(g) ⇌ 2NH3(g) ΔH = −92 kJ mol−1 Equilibrium 24.1

i. Explain how le Chatelier’s principle can be used to predict the conditions of temperature
and pressure for a maximum equilibrium yield of ammonia.

Answer 3

Pressure:
  Right-hand side has fewer (gaseous) moles
  OR 4 (gaseous) moles form 2 (gaseous)
moles ✓

  High pressure ✓

Temperature:
  (Forward) reaction is exothermic/ΔH is
negative
  OR (Forward) reaction gives out heat ✓

  Low temperature ✓

Question 4

State le chateliers principle

Answer 4

The (position of a dynamic) equilibrium shifts to
minimise (the effect of) any change ✔