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Consider the equation below:Cr\(_2\)O\(_7 ^{2-}\) + 6Fe\(^{2+}\) + 14H\(^{+}\) \...


Question

Consider the equation below:

Cr\(_2\)O\(_7 ^{2-}\) + 6Fe\(^{2+}\) + 14H\(^{+}\) \(\to\) 2Cr\(^{3+}\) + 6Fe\(^{3+}\) + 7H\(_2\)O.

The oxidation number of chromium changes from

Options

A) +5 to +3

B) +6 to +3

C) -2 to +3

D) +7 to +3

The correct answer is B.

Explanation:

Cr\(_2\)O\(_7 ^{2-}\) + 6Fe\(^{2+}\) + 14H\(^{+}\) \(\to\) 2Cr\(^{3+}\) + 6Fe\(^{3+}\) + 7H\(_2\)O
The oxidation of Cr in Cr\(_2\)O\(_7 ^{2-}\) :
Let the oxidation of Cr = x; 
2x + (-2 x 7) = -2 \(\implies\) 2x - 14 = -2
2x = 12 ; x = +6
Hence, the change in oxidation of Cr = +6 to +3

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Dicussion (1)

  • Cr\(_2\)O\(_7 ^{2-}\) + 6Fe\(^{2+}\) + 14H\(^{+}\) \(\to\) 2Cr\(^{3+}\) + 6Fe\(^{3+}\) + 7H\(_2\)O
    The oxidation of Cr in Cr\(_2\)O\(_7 ^{2-}\) :
    Let the oxidation of Cr = x; 
    2x + (-2 x 7) = -2 \(\implies\) 2x - 14 = -2
    2x = 12 ; x = +6
    Hence, the change in oxidation of Cr = +6 to +3

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