Video Transcript
The industrial production of
ethanol uses ethene gas and steam, as shown: C2H4 gas plus H2O gas in equilibrium
with C2H5OH gas. Considering that the forward
reaction is exothermic, what effect will increasing the temperature have on the
position of the equilibrium?
When considering what effect
changing different factors will have on the position of equilibrium, we can refer to
Le Chatelier’s principle. The Chatelier’s principle states
for a dynamic equilibrium, if the conditions change, the position of equilibrium
will move to counteract the change. For example, say we had an
equilibrium mixture of two gases; then, we increase the concentration of the
reactant. To counteract this change, the
forward reaction will be favored, causing more reactant particles to react to form
the product, restoring equilibrium. In this case, we can say that the
position of equilibrium will move to the right towards the product side.
In this question, we want to know
what effect increasing the temperature will have on equilibrium. We’re told that the forward
reaction is exothermic. An exothermic reaction is one that
releases energy into the surroundings, which would have the effect of increasing the
temperature. We know that the forward reaction
is exothermic, which as we said would increase the temperature. This implies the backwards reaction
is endothermic, which means that it would absorb energy from the surroundings. This would have the effect of
decreasing the temperature.
If the temperature of the reaction
increases, we know that equilibrium will shift to counteract the change. As the backward reaction will
decrease the temperature, we know that the backward reaction will be favored. So, we can say that the equilibrium
will move to the left. So when the forward reaction is
exothermic, the effect that increasing the temperature will have on the position of
equilibrium is that the equilibrium will move to the left.
