Consider the gas-phase equilibrium A ⇌ B. In a series of experiments, different initial

amounts of A and B are mixed together, and the mixture in each case is allowed to come to
equilibrium. Which one of these experiments would yield values for the amounts of A and B
present at equilibrium different from all the other experiments?
a. 3.0 moles A, 4.5 moles B
b. 4.5 moles A, 3.0 moles B
c. 1.5 moles A, 4.5 moles B
d. 7.5 moles A, no B
e. 0.5 moles A, 7.0 moles B

The answer is given as C....but I have absolutely no idea what is going on here....

answered above.

To determine which experiment would yield values for the amounts of A and B present at equilibrium different from all the other experiments, we need to consider the concept of Le Chatelier's principle.

Le Chatelier's principle states that when a system at equilibrium is subjected to a change in conditions, it will adjust to counteract the imposed change and re-establish equilibrium.

In this gas-phase equilibrium A ⇌ B, if we increase the concentration of A, the system will respond by shifting the equilibrium towards the right, producing more B to counteract the increase in A. Similarly, if we increase the concentration of B, the system will shift the equilibrium towards the left, producing more A.

Now let's analyze each experiment and its impact on the equilibrium:

a. 3.0 moles A, 4.5 moles B: This experiment starts with more B than A. According to Le Chatelier's principle, the system will shift towards the left to produce more A and reduce the excess B.

b. 4.5 moles A, 3.0 moles B: This experiment starts with more A than B. The system will shift towards the right to produce more B and reduce the excess A.

c. 1.5 moles A, 4.5 moles B: This experiment starts with less A and more B. The system will shift towards the right to produce more B and restore the equilibrium. This is the only experiment where we have a lower initial amount of A, making it different from all other experiments.

d. 7.5 moles A, no B: This experiment starts with a high concentration of A and no B. The system will shift towards the left to produce more B and restore the equilibrium.

e. 0.5 moles A, 7.0 moles B: This experiment starts with more B than A. The system will shift towards the left to produce more A and reduce the excess B.

Therefore, experiment c. 1.5 moles A, 4.5 moles B would yield values for the amounts of A and B present at equilibrium different from all the other experiments.

To determine which experiment would yield values for the amounts of A and B different from the others, we need to consider the principles of Le Chatelier's principle and the law of mass action.

Le Chatelier's principle states that when a system at equilibrium is subjected to a change, it will respond by shifting to counteract the effect of the change and reestablish equilibrium. In this case, the system is the gas-phase equilibrium A ⇌ B.

The law of mass action states that the rate of a chemical reaction is proportional to the product of the concentrations of the reactants raised to the power of their stoichiometric coefficients.

Now, let's analyze each experiment and how it affects the equilibrium:

a. 3.0 moles A, 4.5 moles B
b. 4.5 moles A, 3.0 moles B

In both cases a and b, the initial amounts of A and B are in a 1:1 ratio. Therefore, the system will reach equilibrium where the concentrations of A and B are equal, regardless of the initial quantities. These two experiments would yield the same equilibrium values.

c. 1.5 moles A, 4.5 moles B

In experiment c, there is an excess amount of B and a lower amount of A compared to experiments a and b. According to Le Chatelier's principle, the system will shift in the direction that counteracts the change. As a result, the equilibrium will be shifted towards the side with fewer moles, favoring the formation of A. This means that experiment c would yield a different equilibrium composition compared to experiments a and b.

d. 7.5 moles A, no B
e. 0.5 moles A, 7.0 moles B

Experiments d and e involve an extreme imbalance in the initial amounts of A and B. In experiment d, there is no B present initially, which means the system will not be able to reach equilibrium since there is no B to convert to A. Experiment e has an excess of B compared to the other experiments, which will result in more B being present at equilibrium and less A.

Therefore, the experiment that would yield different equilibrium values for the amounts of A and B compared to the others is experiment c: 1.5 moles A, 4.5 moles B.