Question

The reaction: Citrate ⇌ cis-Aconitate + H2O, starting from a pure citrate solution reaches equilibrium. The osmotic pressure was π0 = 0.0019 atm at the beginning of the reaction, and changed to πeq = 0.0036 atm after reaching equilibrium. The temperature is T = 37 C. What is the Gibbs free energy of the reaction if the total concentration of products is 600 times greater than the concentration of the reactant?

I know that you would use G =Go +RTlnQ, but am not sure how the osmotic pressures figure in. Thank you in advance!

Answer 1

From the formula we can conclude that

To find Q we need concentration of products and reactants

we also know osmotic pressure formula which is

π = CRT

initially only reactant is present

so C= π/RT = .0019/(.082*310)= 0000747 mol/l

Ceq = .0036/.082*310= 0.0001416

Also product conc = 600* reactant conc

so 0.0001416 = 601 c

conc of product= 2.35* 10^-7

conc of each product = 300* 2.35* 10^-7 = 0.0000705

delta G = - 8.314 * 310 * Ln(0.0000705^2/2.35* 10^-7)

Delta G = 9938.52