The signs of DG, DH, and DS at 25°C are shown in the table below for three reactions.

Reaction DG DH DS
I - + +
II - - +
III - - -

Which reaction or reactions should go in the REVERSE direction at high temperature?

Here is what I did for #1.

delta G = delta H - T*delta S
delta G -
delta H +
delta S +
For high T, -Tdelta S is more negative which makes delta G more negative. Since it is already negative, raising T won't change the direction.
I think reaction ii and iii are done the same.

To determine which reaction or reactions should go in the reverse direction at high temperature, we need to consider the sign of the change in Gibbs Free Energy (ΔG), Enthalpy (ΔH), and Entropy (ΔS).

At high temperatures, the ΔG value becomes less negative or even positive, favoring the reverse reaction. This can occur when ΔH and ΔS have different signs.

Looking at the table:

- Reaction I has a negative ΔG, positive ΔH, and positive ΔS. The positive ΔH suggests an endothermic reaction, while the positive ΔS indicates an increase in disorder. These factors are consistent with the forward reaction, so Reaction I should not go in the reverse direction at high temperature.

- Reaction II has a negative ΔG, negative ΔH, and positive ΔS. The negative ΔH suggests an exothermic reaction, while the positive ΔS indicates an increase in disorder. These factors are consistent with the forward reaction, so Reaction II should not go in the reverse direction at high temperature.

- Reaction III has a negative ΔG, negative ΔH, and negative ΔS. The negative ΔH suggests an exothermic reaction, while the negative ΔS indicates a decrease in disorder. These factors are consistent with the forward reaction. However, at high temperatures, the negative ΔS makes the ΔG value less negative or even positive, favoring the reverse reaction. Therefore, Reaction III should go in the reverse direction at high temperature.

In summary, Reaction III should go in the reverse direction at high temperature.

To determine which reactions should go in the reverse direction at high temperature, we need to consider the signs of the changes in Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS). The reverse direction of a reaction is favored when it becomes more exothermic, has a decrease in entropy, and has a positive change in Gibbs free energy.

Looking at the given table, we can analyze each reaction:

Reaction I:
- ΔG: Negative
- ΔH: Positive
- ΔS: Positive

Reaction II:
- ΔG: Negative
- ΔH: Negative
- ΔS: Positive

Reaction III:
- ΔG: Negative
- ΔH: Negative
- ΔS: Negative

Based on these signs, we can infer the following:

1. Reaction I:
- It has a positive ΔH and DS, indicating that the forward direction is favored at high temperatures (as the positive term TΔS counteracts the ΔH term).

2. Reaction II:
- It has a negative ΔH and a positive ΔS, indicating that the forward direction is favored at high temperatures (as the positive term TΔS counteracts the ΔH term).

3. Reaction III:
- It has a negative ΔH and ΔS, which means that the reverse direction is favored at high temperatures since the negative term TΔS dominates over the ΔH term.

Therefore, Reaction III should go in the REVERSE direction at high temperature.