CHEM 340 HSTC Physical Chemistry for Biochemists Questions
Chemistry 340 Physical Chemistry for Biochemists IFall 2022
HOMEWORK SET No. 10
This homework set is due on Tuesday, November 22, 2022
1. How much work is required to bring two protons from an infinite distance of separation to 0.1 nm?
Calculate the answer in joules using the protonic charge 1.602 × 10−19 C . What is the work in kJ
mol-1 for a mole of proton pairs?
2. A small dry battery of zinc and ammonium chloride weighing 85 g will operate continuously
through a 4-Ω resistance for 450 min before its voltage falls below 0.75 V. The initial voltage is
1.60 V, and the effective voltage over the whole life of the battery is taken to be 1.00 V.
Theoretically, how many kilometers above the earth could this battery be raised by the energy
delivered under these conditions?
3. Calculate the energy in kJ mol−1 required to separate a positive and negative charge from 0.3 nm
to infinity in (a) a vacuum, (b) a solvent of dielectric constant 10, and (c) water at 25 °C, which
has a dielectric constant of approximately 80.
4. The solubility of Ag2CrO4 in water is 8.00 × 10−5 mol kg -1 at 25 °C, and its solubility in 0.04 mol
kg-1 NaN03 is 8.84 × 10−5 mol kg -1 . What is the mean ionic activity coefficient of Ag2CrO4 in 0.04
mol kg-1 NaNO3?
5. Estimate the electromotive force of the cell Zn(s)|ZnCl2(aq,0.02 mol kg-1)|AgCl(s)|Ag(s) at 25 °C
using the Debye-Hückel theory.
6. Design cells without liquid junction that could be used to determine the activity coefficients of
aqueous solutions of (a) NaOH and (b) H2SO4. Give the equations relating electromotive force to
the mean ionic activity coefficient at 25 °C.
7. For the galvanic cell
H 2 (1 bar ) HCl ( ai ) Cl2 ( l bar )
the standard electromotive force at 298.15 K is 1.3604 V and ( ∂E ° / ∂T ) P =
− 1.247 ×10−3 VK −1 .
(a) For the cell reaction, what are the values of ΔrG0, ΔrH°, ΔrS°? (b) For Cl-(ao) what are the
values of ΔrG°, ΔrH°, and S°?
8. Use Appendix C.2 to calculate the standard electrode potential for Cl-lAgCl(s)|Ag at 90 °C if
∆ r Cp° = 0 .
