Question

The density of the fat tristearin is 0.95 g cm−3 . Calculate the change in molar Gibbs energy of tristearin when a deep-sea creature is brought to the surface (p = 1.0 atm) from a depth of 2.0 km. To calculate the hydrostatic pressure, take the mean density of water to be 1.03 g cm−3 .

Answer 1

The formula for the change in Gibbs energy of a solid is:

ΔG = Vm ΔP

where, ΔG is change in Gibbs, Vm is molar volume, ΔP is change in pressure

ΔP = P(final) – P(initial)

P(final) = 1 atm = 101325 Pa

P(initial) = ρ_water *g *h = (1030 kg/m^3) * 9.8 m/s^2 * 2000 m = 20188000 kg m/s^2 = 20188000 Pa

Vm = (950 kg/m^3) * (1000 mol / 891.48 kg) = 1065.64 mol/m^3

 

So,

ΔG = (1065.64 mol/m^3) * (101325 Pa - 20188000 Pa)

ΔG = -21405164347 J = -21.4 GJ