For the reaction:

2A(g) + B(g) → 2D(g)

At 298 K:

ΔU° = −10 kJ mol⁻¹
ΔS° = −44 J K⁻¹ mol⁻¹

Given R = 8.31 J mol⁻¹ K⁻¹,
find ΔG° for the reaction and determine whether the reaction is spontaneous at 298 K.

Which of the following statements is correct for an irreversible isothermal expansion of an ideal gas?

1. $∆\mathrm{U}=0,<mspace\; width="1em"></mspace>∆{\mathrm{S}}_{\mathrm{total}}\ne 0$

2. $∆\mathrm{U}\ne 0,<mspace\; width="1em"></mspace>∆{\mathrm{S}}_{\mathrm{total}}=0$

3. $∆\mathrm{U}=0,<mspace\; width="1em"></mspace>∆{\mathrm{S}}_{\mathrm{total}}=0$

4. $∆\mathrm{U}\ne 0,<mspace\; width="1em"></mspace>∆{\mathrm{S}}_{\mathrm{total}}\ne 0$

If for a certain reaction ${∆}_{r}H$ is 30 kJ mol^–1 at 450 K, the value of ${∆}_{r}S$ (in JK^–1 mol^–1) for which the same reaction will be spontaneous at the same temperature is: