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chemistry igcse acapprinted 61 · PDF 61
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- Increasing the concentration of either iodine monochloride (ICl) or chlorine gas (Cl₂) will cause
the position of equilibrium to shift to the right-hand side, thereby increasing the yield of iodine
trichloride (ICl₃).
- Decreasing the concentration of either iodine monochloride (ICl) or chlorine gas (Cl₂) will cause
the position of equilibrium to shift to the left-hand side, thereby decreasing the yield of iodine
trichloride (ICl₃).
Equilibrium and Rate of Reaction
- Do not confuse the effects of temperature, pressure, and concentration on the rate of reaction
with their effects on the position of equilibrium.
- While an increase in temperature may favor the endothermic reaction and not the exothermic
reaction, it will still increase the rate of reaction for both the exothermic and endothermic
reactions.
- While an increase in pressure may favor the side with fewer moles and not the side with more
moles, it will still increase the rate of reaction for both the forward and backward reactions.
- While an increase in concentration may favor the opposite side to where the concentration was
increased and not the other side, it will still increase the rate of reaction for both the forward and
backward reactions.
- Adding a catalyst will only increase the speed/rate of both the forward and backward reactions. It
has no effect on the position of equilibrium.
- Industries often use an optimum/compromised temperature and pressure. While increasing the
temperature may decrease the yield of the product industries are trying to produce, it also increases
the rate of reaction at which this product forms. Similarly, pressure may have the same effect
depending on the product.
- If industries were to use too low of a temperature (similarly with pressure) just to increase the
yield of the product, the reaction would be extremely slow. If they were to use too high of a
temperature (similarly with pressure) just to increase the speed of the reaction, the yield of the
product would be extremely low.
- Thus, there is an optimum temperature and pressure for most chemical reactions. These are the
temperatures and pressures at which the yield of the product and the speed of the reaction are
balanced.