Calculate ΔG for Dilution of HCl from 0.89M to 0.253M

[salman213]

1. Calculate ΔG for the dilution of aqueous HCl from 0.89 M to 0.253 M at 25°C.

data



2. The process you are considering is:
H+(aq) + Cl-(aq)® H+(aq) + Cl-(aq) (for which ΔG°=0 i.e. standard states all round--both sides are the same).
Now use ΔG=ΔG° + RTln(Q). (Use the actual concentrations to determine Q).
Does this agree with what you intuitively know about the spontaneity of diffusion?



3.

DeltaG = (8.314)(298.15)(ln (0.253)) - (8.314)(298.15)(ln(0.89)) = -3117.9 J/mol

but this is wrong??

 

[Nino MMP]

Yes, this is incorrect. The correct calculation is: DeltaG = (8.314)(298.15)(ln(0.89/0.253)) = -3117.9 J/mol. This agrees with what we intuitively know about the spontaneity of diffusion - that it is more likely to occur spontaneously when the concentrations of the reactants become more dilute.

 

[Blueshift5]

It appears that the calculation was done incorrectly. The correct calculation should be ΔG = (8.314)(298.15)(ln (0.253/0.89)) = -3117.9 J/mol. This result indicates that the dilution of HCl from 0.89M to 0.253M is a spontaneous process at 25°C, as the ΔG value is negative. This agrees with our intuition that diffusion is a spontaneous process, as the concentration gradient between the two solutions will drive the movement of particles from higher to lower concentration.