PCl₅(g) ⇌ PCl₃(g) + Cl₂(g) is endothermic…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
is endothermic. Predict the effect on the amount of at equilibrium, and on , of: (a) adding chlorine; (b) raising the temperature; (c) halving the volume; (d) adding argon at constant volume; (e) adding a catalyst.
Need a reminder? The key ideaShow
Le Chatelier: a disturbed equilibrium shifts to undo part of the change. Adding a reactant or removing a product shifts it forward. Higher pressure favours fewer moles of gas. Heating favours the endothermic direction and changes K. A catalyst does not shift the equilibrium.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Adding chlorine. A product is added, so the mixture shifts backward. Less ; K unchanged.
Step 2. Heating. The forward reaction is endothermic, so K rises. More .
Step 3. Halving the volume. The pressure rises, so the mixture shifts towards one mole of gas, backward. Less ; K unchanged.
Step 4. Argon at constant volume. The concentrations of the reacting gases do not change. No shift.
Step 5. A catalyst. No shift; equilibrium is reached sooner.
Answer: less, more, less, no change, no change. Only heating changes K.
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