In acidic medium, dichromate ion oxidizes ferrous ion to ferric ion. If the gram molecular weight of potassium dichromate is ` 294 g`, is gram equivalent weight is `"______" g`.

Options

A. ` 294`
B. ` 127`
C. `49`
D. ` 24.5`

Answer

C

Explanation

Equivalent mass of oxidizing agent
`=("Formula mass")/(("Total change in oxidation number of element"),("oxidized or reduced per mole of compound"))`
`overset(+6)(C)r_(2)O_(7)^(2-) rarr 2overset(+3)(C)r^(3+)`
The total change in oxidation number (For two Cr atoms ) is of ` 6 ` units ( +12 to 6 ). Thus,
Equvalent mass `= (296)/6 = 49`
Here students often make the mistake of dividing formula mass by 3 as they calculate the change in oxidation number for just one Cr atom.