Consider the graph of concentration vs time shown below for the reaction:
2SO2(g) + O2(g) 2SO3(g)
Show what changes would occur in the concentrations of all three species if the volume of the reaction vessel was suddenly increased.
If the volume of the reaction vessel is suddenly increased, the concentrations of all three species will decrease.
According to Le Chatelier's principle, when the volume of a system is increased, the system will try to minimize the effect of the change by shifting in the direction that produces fewer gas molecules. In this reaction, the total number of moles of gas on the left side is 3 (2 moles of SO2 + 1 mole of O2), while the total number of moles of gas on the right side is 2 (2 moles of SO3). Therefore, the reaction will shift to the left to decrease the total number of moles of gas.
As the reaction shifts to the left, the concentrations of SO2, O2, and SO3 will all decrease. The decrease in concentration will be more significant for the products (SO3) compared to the reactants (SO2 and O2) as the reaction shifts to the left to decrease the gas concentration.
Overall, the concentrations of all three species will decrease if the volume of the reaction vessel is suddenly increased.
When the volume of the reaction vessel is suddenly increased, the system will shift to restore equilibrium. In this case, according to Le Chatelier's principle, the concentrations of the three species, SO2, O2, and SO3, will change in response to the change in volume.
Since the volume is increased, the system will try to counteract this change by increasing the total number of gas molecules. This can be achieved by shifting the equilibrium towards the side with more gas molecules (in this case, the right side).
To do this, the concentrations of SO2 and O2 will decrease, while the concentration of SO3 will increase. The reaction will proceed in the forward direction to produce more SO3 to compensate for the increase in volume.
In summary, the changes in concentrations would occur as follows:
1. Concentration of SO2: Decrease
2. Concentration of O2: Decrease
3. Concentration of SO3: Increase
To determine the changes in the concentrations of all three species (SO2, O2, and SO3) when the volume of the reaction vessel is suddenly increased, we need to understand the effect of changing the volume on the equilibrium position.
When the volume of the reaction vessel is increased, according to Le Chatelier's principle, the equilibrium will shift in the direction that produces more gas molecules. In this case, the forward reaction (formation of SO3) produces two gas molecules, while the reverse reaction (formation of SO2 and O2) only produces three gas molecules.
Thus, increasing the volume will favor the side of the reaction with more gas molecules, i.e., the forward reaction. As a result, the concentration of SO2 and O2 will decrease, while the concentration of SO3 will increase.
Let's break down the steps to determine the changes in concentration:
Step 1: Write the balanced chemical equation and determine the stoichiometry:
2SO2(g) + O2(g) ⇌ 2SO3(g)
Step 2: Identify the initial concentrations of the reactants and the product:
- [SO2]i = initial concentration of SO2
- [O2]i = initial concentration of O2
- [SO3]i = initial concentration of SO3
Step 3: Analyze the changes in concentration:
- [SO2]f = final concentration of SO2 (after the volume increase)
- [O2]f = final concentration of O2 (after the volume increase)
- [SO3]f = final concentration of SO3 (after the volume increase)
Step 4: Apply Le Chatelier's principle to determine the changes in concentration:
- Since the volume increase favors the forward reaction, the concentration of SO2 and O2 will decrease.
- The concentration of SO3, on the other hand, will increase as a result of the volume increase.
Therefore, after the volume increase, the concentrations of SO2 and O2 will decrease, and the concentration of SO3 will increase.
It's important to note that without specific information about the initial concentrations and actual volume change, we cannot determine the exact numerical changes in concentration. The above explanation provides a generalized understanding of the effect of a volume increase on the concentrations in the reaction.