Heat from fire or heat from the sun warming your face
Explanation :
As we know that the Gibbs free energy is not only function of temperature and pressure but also amount of each substance in the system.

where,
is the amount of component 1 and 2 in the system.
Partial molar Gibbs free energy : The partial derivative of Gibbs free energy with respect to amount of component (i) of a mixture when other variable
are kept constant are known as partial molar Gibbs free energy of
component.
For a substance in a mixture, the chemical potential
is defined as the partial molar Gibbs free energy.
The expression will be:

where,
T = temperature
P = pressure
is the amount of component 'i' and 'j' in the system.
a. 48.6 is magnesium and 32.0 is oxygen
b. 80.6
c. also 80.6
d. yes, because the product has equal mass to the reactants
Use the clapeyron equation:
T in kelvin : 6.80 + 273 => 279.8 K
R = 0.082
n = 71.5 moles
P = 5.03 atm
Therefore:
P x V = n x R x T
5.03 x V = 71.5 x 0.082 x 279.8
5.03 x V = 1640.4674
V = 1640.4674 / 5.03
V = 326.13 L
hope ths helps!