1. Give reasons for your choice. 2. Give reasons for rejecting other options.
The reaction
C(s) + O2(g) CO2(g) + heat
reaches equilibrium in a closed reaction vessel.
Which one of the following actions causes the
equilibrium to shift to the right ?
A increasing the volume of the reaction vessel
B adding a catalyst
C adding a small amount of carbon
D lowering the temperature
E increasing the reaction time
d. Lowering temp means removing heat.
To determine which action causes the equilibrium to shift to the right, we need to understand Le Chatelier's Principle. This principle states that when a system at equilibrium is subjected to a change, it will adjust itself in a way that counteracts the change and restores equilibrium.
In the given reaction: C(s) + O2(g) ⇌ CO2(g) + heat
1. Increasing the volume of the reaction vessel (Option A):
According to Le Chatelier's Principle, increasing the volume of the reaction vessel will shift the equilibrium in the direction that produces more gas molecules. In this case, the reaction produces one molecule of CO2, whereas both C and O2 are solids and gases, respectively. Increasing the volume will decrease the pressure, causing the equilibrium to shift towards the side with a higher number of gas molecules. Therefore, the equilibrium will shift to the right.
2. Adding a catalyst (Option B):
A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It does not affect the position of the equilibrium. Therefore, adding a catalyst will not shift the equilibrium.
3. Adding a small amount of carbon (Option C):
Adding carbon (C) to the system will increase the concentration of one of the reactants. According to Le Chatelier's Principle, increasing the concentration of a reactant will cause the equilibrium to shift in the direction that consumes the added substance. In this case, adding carbon will shift the equilibrium to the left, not to the right.
4. Lowering the temperature (Option D):
Decreasing the temperature will cause the equilibrium to shift in the exothermic direction, which is the direction that gives off heat. In this case, the forward reaction is exothermic, so lowering the temperature will favor the forward reaction (to the right) to produce more heat and restore equilibrium.
5. Increasing the reaction time (Option E):
Increasing the reaction time does not affect the equilibrium position. The reaction time refers to the duration for which the reaction is allowed to proceed. It does not play a role in shifting the equilibrium.
In conclusion, the action that causes the equilibrium to shift to the right is option D, lowering the temperature. The other options do not shift the equilibrium towards the right.