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181. Write the Nernst equation and emf of the following cells at 298 k.
Mg(s) | Mg²⁺ (0.001 M) || Cu²⁺ (0.0001 M) | Cu(s)

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Anode reaction:

Fe (s) \to {Fe}^{2 +} (aq) + 2 e^{-}

Cathode reaction:

2 H^{+} + 2 e^{-} \to H_{2} (g)

Overall cell reaction:

Fe (s) + 2 H^{+} (aq) \to {Fe}^{2 +} (aq) + H_{2} (g) Here, n = 2, {E^{0}}_{cell} = {E^{0}}_{cathode} - {E^{0}}_{anode} = 0 - (- 0.44 V) = + 0.44 V .

The Nernst equation for E_cell at 298 k can be written as:

E_{cell} = {E^{0}}_{cell} - \frac{0.059}{n} \log \frac{[{Fe}^{2 +}]}{[H^{+}]} = 0.44 - \frac{0.059}{n} \log \frac{10^{- 3}}{1} = 0.44 - \frac{0.0591}{2} (- 3)

= 0.44 – 0.0295 (–3) = 0.44 – 0.0885 = 0.5285 V

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183. Write the Nernst equation and emf of the following cells at 298 k.
Sn(s) | Sn²⁺ (0.050 M) || H⁺(0.020 M) H₂(g) (1bar) Pt (s)

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184. Write the Nernst equation and emf of the following cells at 298 k.
Pt(s) | Br₂ (l) | Br^– (0.010 M) || H⁺ (0.030 M) | + H₂(g) (1 bar) | Pt(s).

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185. What is corrosion? What are the factors which affect corrosion?

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186. CO₂ is always present in natural water. Explain its effect (increases, stops or no effect) on rusting of iron.

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187. Rusting of iron is quicker in saline water than in ordinary water. Explain.

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188. We can use aluminium in place of zinc for cathodic protection of rusting. Comment.

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189. How is cathodic protection of Iron different from its galvanisation?

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190. Define conductivity and molar conductivity for the solution of an electrolyte. Discuss their variaion with concentration.

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