CBSE Class 12 · 2005 · Delhi Compartment · Redox Reactions and ElectrochemistryShort Answer

What is corrosion? Describe the electrochemical phenomenon of rusting of iron.

Solution

Corrosion is the slow deterioration of a metal by reaction with atmospheric oxygen, moisture and other gases, converting the surface metal into its oxide, carbonate or sulphide — e.g. rusting of iron, tarnishing of silver.
Rusting of iron is electrochemical: the water film on iron acts as the electrolyte.
Anodic spots:

Fe ⟶ F e^{2 +} + 2 e^{-}

Cathodic spots (H

^{+}

from dissolved CO

_{2}

O_{2} + 4 H^{+} + 4 e^{-} ⟶ 2 H_{2} O

The Fe

^{2 +}

ions migrate, are oxidised by air to Fe

^{3 +}

, and deposit as hydrated ferric oxide,

F e_{2} O_{3} \cdot x H_{2} O (rust)

CBSE Class 12 Board · 2005 · Delhi Compartment · Subjective

Practise more: all CBSE board PYQs on Redox Reactions and Electrochemistry →

More board questions on Redox Reactions and Electrochemistry

Which of the following cells is used in the Apollo space programme?
CBSE 2024View solution →
Dilution affects both conductivity as well as molar conductivity. The effect of dilution on both is as follows:
CBSE 2024View solution →
State the following:
(a) Kohlrausch law of independent migration of ions
(b) Faraday's first law of electrolysis
CBSE 2024View solution →
The resistance of a conductivity cell filled with 0.2 mol L $^{- 1}$ KCl solution is 200 Ω. If the resistance of the same cell when filled with 0.05 mol L $^{- 1}$ KCl solution is 620 Ω, calculate the conductivity and molar conductivity of the 0.05 mol L $^{- 1}$ KCl solution. The cond …
CBSE 2024View solution →
Calculate the emf of the following cell:
$Ni (s) + 2A g^{+} (0.01 M) ⟶ N i^{2 +} (0.1 M) + 2Ag (s)$

Given: $E_{ce l l}^{\circ} = 1.05$ V, log 10 = 1.
CBSE 2024View solution →
Which one of the following cells was used in the Apollo space programme?
CBSE 2023View solution →