Electrochemistry

Question

The emf of a cell corresponding to the reaction
Zn(s) + 2H⁺ (aq) → Zn²⁺ (0.1 M) + H²(g) (1 atm) is 0.28 V at 15° C.Write the half cell reactions and calculate the pH of the solution at the hydrogen electrode.

Solution

We have given the cell reaction
Zn(s) + 2H⁺ (aq) → Zn²⁺ (0.1 M) + H²(g) (1 atm)
thus

{E^{0}}_{{Zn}^{2 +} / Zn} = - 0.76 V, {E^{0}}_{H^{+} / H_{2}} = 0

Half call reaction will be

{Zn}^{2 +} + 2 e^{-} \to Zn

...(i)

H^{+} + e^{-} = \frac{1}{2} H_{2}

2 H^{+} + 2 e^{-} \to H^{2}

...(ii)

E_{Zn / {Zn}^{2 +}} = E °_{Zn / {Zn}^{2 +}} - \frac{RT}{nF} \ln \frac{[{Zn}^{2 +}]}{[Zn]}

Here

R = 8.314 J {mol}^{- 1} \log^{- 1}, T = 298 K, F = 96500 coulomb n = 2, {E^{0}}_{Zn / {Zn}^{2 +}} = 0.76 .

Therefore,

E_{Zn / {Zn}^{2 +}} = 0.76 - \frac{8.314 \times 298}{2 \times 96500} \ln \frac{0.1}{1} = 0.79 V

Similarly,

E_{H^{+} / H_{2}} = {E^{0}}_{H^{+} / H_{2}} - \frac{RT}{nF} \ln \frac{[H_{2}]}{{[H^{+}]}^{2}} = 0 - \frac{0.314 \times 298}{2 \times 96500} \ln \frac{[I]}{{[H^{+}]}^{2}} = 0.05915 \log_{10} [H^{+}] = 0.05915 pH [∴ - \log_{10} [H^{+}] = pH]

Now since

E = E_{Zn / {Zn}^{2 +}} + E_{H^{+} / H_{2}} = 0.28 = 0.79 - 0.05915 pH pH = \frac{0.15}{0.05915} = 8.62 .

Some More Questions From Electrochemistry Chapter

The molar conductivity of 0.025 mol L^–1methanoic acid is 46.1 S cm² mol^–1. Calculate its degree of dissociation and dissociation constant. Give λ°(H⁺) = 349.6 S cm²mol^–1 and λ° (HCOO^– ) = 54.6 s cm² mol^–1.

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Electrochemistry

The emf of a cell corresponding to the reaction
Zn(s) + 2H⁺ (aq) → Zn²⁺ (0.1 M) + H²(g) (1 atm) is 0.28 V at 15° C.Write the half cell reactions and calculate the pH of the solution at the hydrogen electrode.

Some More Questions From Electrochemistry Chapter

The molar conductivity of 0.025 mol L^–1methanoic acid is 46.1 S cm² mol^–1. Calculate its degree of dissociation and dissociation constant. Give λ°(H⁺) = 349.6 S cm²mol^–1 and λ° (HCOO^– ) = 54.6 s cm² mol^–1.

If the current of 0.5 ampere flows through a metallic wire for 2 hours, then how many electrons flow through the wire?

Suggest a list of metals that are extracted electrolytically.

Consider the reaction: Cr₂O₇^2– + 14H⁺ + 6e- → 2Cr³⁺ + 8H₂O
What is the quantity of electricity in coulombs needed to reduce 1 mol of Cr₂O₇^2-?

Write the chemistry of recharging the lead storage battery, highlighting all the materials that are involved during recharging.

Suggest two materials other than hydrogen that can be used as fuels in fuel cells.

Name the electrolyte used in fuel cell?

Can we use copper vessel to store AgNO₃solution ?

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NCERT Sample Papers

Entrance Exams Preparation

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For Daily Free Study Material Join wiredfaculty

Electrochemistry

The emf of a cell corresponding to the reactionZn(s) + 2H+ (aq) → Zn2+ (0.1 M) + H2(g) (1 atm) is 0.28 V at 15° C.Write the half cell reactions and calculate the pH of the solution at the hydrogen electrode.

Some More Questions From Electrochemistry Chapter

The molar conductivity of 0.025 mol L–1 methanoic acid is 46.1 S cm2 mol–1. Calculate its degree of dissociation and dissociation constant. Give λ°(H+) = 349.6 S cm2 mol–1 and λ° (HCOO– ) = 54.6 s cm2 mol–1.

If the current of 0.5 ampere flows through a metallic wire for 2 hours, then how many electrons flow through the wire?

Suggest a list of metals that are extracted electrolytically.

Consider the reaction: Cr2O72– + 14H+ + 6e- → 2Cr3+ + 8H2OWhat is the quantity of electricity in coulombs needed to reduce 1 mol of Cr2O72-?

Write the chemistry of recharging the lead storage battery, highlighting all the materials that are involved during recharging.

Suggest two materials other than hydrogen that can be used as fuels in fuel cells.

Name the electrolyte used in fuel cell?

Can we use copper vessel to store AgNO3 solution ?

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

The emf of a cell corresponding to the reaction
Zn(s) + 2H⁺ (aq) → Zn²⁺ (0.1 M) + H²(g) (1 atm) is 0.28 V at 15° C.Write the half cell reactions and calculate the pH of the solution at the hydrogen electrode.

The molar conductivity of 0.025 mol L^–1methanoic acid is 46.1 S cm² mol^–1. Calculate its degree of dissociation and dissociation constant. Give λ°(H⁺) = 349.6 S cm²mol^–1 and λ° (HCOO^– ) = 54.6 s cm² mol^–1.

Consider the reaction: Cr₂O₇^2– + 14H⁺ + 6e- → 2Cr³⁺ + 8H₂O
What is the quantity of electricity in coulombs needed to reduce 1 mol of Cr₂O₇^2-?

Can we use copper vessel to store AgNO₃solution ?