3.1k views
1 vote
Calculate the value of the solubility product constant for PbSO4 from the half-cell potentials. PbSO4(s) + 2e- → Pb(s) + SO42-(aq) Eº = -0.351 V Pb2+ + 2e- → Pb(s) Eº = -0.130 V

1 Answer

2 votes

Answer:

K s p = 3.37 × 10 ⁻⁸

Step-by-step explanation:

Anode (oxidation) half reaction:

P b (s) → Pb²⁺(aq) + 2e⁻ E° = 0.130 V

Cathode (reduction) half reaction:

PbSO₄(s) + 2e- → Pb(s) + SO₄²⁻(aq) Eº = -0.351 V

Adding the two half reactions together gives a net reaction equivalent to the solubility equilibrium of lead (II) sulfate salt:

PbSO₄(s) → Pb²⁺ + SO₄²⁻(aq)

Ksp = [Pb²⁺] [SO₄²⁻]

E ° c e l l = 0.130 - 0.351 = − 0.221 V

using the Nernst equation; -RTlnK = − n F E ° c el l

where R is molar gas constant, T is temperature, n is number of moles of electron, F is Faraday's constant,

-RTlnK = − ( 2 m o l ) ( 96485 C / m o l ) ( − 0.221 V )

-RTlnK = -42646 J / m o l

ln K = lnK s p = -( 42646 / R T)

lnK s p = -( 426466/ 8.314 × 298.15 )

Ksp = e∧(-17.204)

K s p = 3.37 × 10 ⁻⁸

User Brett Y
by
3.8k points