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

# 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

## 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