The position of equilibrium
1 mark · NormalFor the equilibrium reaction:
The forward reaction is exothermic. What will happen to the concentration of PCl5 if the temperature is increased at constant pressure?
- A.It will increase.
- B.It will decrease.
- C.It will stay the same.
- D.It will fluctuate.
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Show answer
Correct option: It will decrease.
Common mistakes: Choosing increase because reaction is exothermic
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Marking points
B1 · 1 mark · Selects 'It will decrease.' as the effect of increasing temperature on the concentration of PCl5 when the forward reaction is exothermic.
Worked solution
Since the forward reaction is exothermic, increasing temperature shifts equilibrium towards the reverse reaction (which absorbs heat), decreasing the concentration of PCl5.