Consider the following chemical equilibrium:
SO3(g) --> SO2(g) + 1/2 O2(g) and Delta H = 98.9J
i. adding oxygen gas
ii. compressing the system at constant temperature
iii. adding argon gas
iv. removing sulfur dioxide gas
v. decreasing the temperature
Which of the above (i-v) will decrease the value of K?
my answer is v. decreasing in temp. is it correct?
yes
To determine which of the given changes will decrease the value of the equilibrium constant (K), we need to consider Le Chatelier's principle. This principle states that if a system at equilibrium is subjected to a stress, it will respond by shifting in a direction that minimizes the effect of that stress.
In this chemical equilibrium, the reaction is exothermic, as indicated by the negative value of ΔH. Therefore, we can recall that increasing the temperature favors the endothermic reaction and decreases the value of K, while decreasing the temperature favors the exothermic reaction and increases the value of K.
Let's consider each of the given changes and their effects on the equilibrium:
i. Adding oxygen gas (O2):
Since O2 appears as a product in the forward reaction, adding more O2 would increase the concentration of products and cause a shift in the reverse direction. This would decrease the value of K.
ii. Compressing the system at constant temperature:
Compressing the system increases the pressure. In this chemical equation, pressure does not affect the number of moles of gas, so it will not have an effect on the equilibrium constant value (K).
iii. Adding argon gas (Ar):
Argon is an inert gas that does not participate in the reaction. Adding an inert gas has no effect on the equilibrium position and, consequently, no effect on the value of K.
iv. Removing sulfur dioxide gas (SO2):
Since SO2 is a reactant, removing it would cause a shift towards the side with the reactants to replace what was lost. This means the reaction would shift in the forward direction, increasing the concentration of products and increasing the value of K.
v. Decreasing the temperature:
As mentioned earlier, decreasing the temperature favors the exothermic reaction. The system would shift towards the exothermic reaction to try to counteract the decrease in temperature, increasing the concentration of products. This would increase the value of K.
Based on the explanation above, your answer is partially correct. The changes in (i) adding oxygen gas and (v) decreasing the temperature will both decrease the value of K.