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chemistry igcse acapprinted 60 · PDF 60
145 pagesrevision 46934
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• Increasing the temperature would favour the endothermic reaction. In this
case, this would cause the position of equilibrium to shift to the left-hand side,
thereby decreasing the yield of ethanol .
• Decreasing the temperature would favour the exothermic reaction. In this
case, this would cause the position of equilibrium to shift to the right-hand
side, thereby increasing the yield of ethanol .
(ii) Pressure (for gases only)
• An increase in pressure favours the side with fewer moles of gases, while a
decrease in pressure favours the side with more moles of gases. Let us take the
same example as before,
- The left-hand side has 1 mole of ethene gas (C₂H₄) and 1 mole of water vapor (H₂O), therefore it
has 2 moles in total. The right-hand side has only 1 mole of ethanol vapor (C₂H₅OH).
- Increasing the pressure would favor the side with fewer moles of gases. In this case, this would
cause the position of equilibrium to shift to the right-hand side, thereby increasing the yield of
ethanol vapor (C₂H₅OH).
- Decreasing the pressure would favor the side with more moles of gases. In this case, this would
cause the position of equilibrium to shift to the left-hand side, thereby decreasing the yield of
ethanol vapor (C₂H₅OH).
(iii) Concentration
- An increase in concentration favors the opposite side to where the concentration was increased,
and a decrease in concentration favors the opposite side to where the concentration was decreased.
For example:
Iodine monochloride (ICl) + chlorine gas (Cl₂) ⇌ iodine trichloride (ICl₃)