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

In summary, the process of diluting aqueous HCl from 0.89 M to 0.253 M at 25°C has a ΔG of -3117.9 J/mol, which agrees with our understanding of the spontaneity of diffusion.
  • #1
salman213
302
1
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??
 
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  • #2
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.
 
  • #3



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.
 

1. What is ΔG?

ΔG, or Gibbs free energy, is a measure of the amount of energy available to do work in a thermodynamic system.

2. How is ΔG calculated for dilution of a solution?

ΔG for dilution can be calculated using the equation ΔG = -RTln(V2/V1), where R is the gas constant, T is the temperature in Kelvin, V2 is the final volume, and V1 is the initial volume of the solution.

3. What is the significance of dilution in calculating ΔG?

Dilution affects the concentration of a solution, which in turn affects the value of ΔG. As the concentration decreases, the value of ΔG becomes more negative, indicating an increase in the amount of available energy.

4. Can ΔG be negative for dilution?

Yes, ΔG can be negative for dilution if the final volume is greater than the initial volume. This indicates that the process is spontaneous and releases energy.

5. How does the dilution of HCl from 0.89M to 0.253M affect ΔG?

The dilution of HCl from 0.89M to 0.253M decreases the concentration of the solution and therefore makes ΔG more negative. This means that the process is spontaneous and releases energy.

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