Question

In acidic medium, dichromate ion oxidises ferrous ion to ferric ion. If the gram molecular weight of potassium dichromate is 294 g, its gram equivalent weight is ...... g.

• A. 294
• B. 147
• C. 49
• D. 24.5

Answer 1

Answer: (C)

49

Answer 2

The reaction of dichromate ion with ferrous ion in acidic medium takes place as: $6F{{e}^{2+}}+C{{r}_{2}}O_{7}^{2-}+14{{H}^{+}}\xrightarrow{{}}$ $6{{F}^{3+}}+2C{{r}^{3+}}+7{{H}_{2}}O$ Total change in oxidation state of iron is $\overset{+12}{\mathop{6F{{e}^{2+}}}}\,\xrightarrow{{}}\overset{+18}{\mathop{6F{{e}^{3+}}}}\,$ Total change = + 6 So, gram equivalent weight of ${{K}_{2}}C{{r}_{2}}{{O}_{7}}$ $\text{=}\,\,\frac{\text{294}}{\text{Total}\,\text{change}\,\text{in}\,\text{O}\text{.S}}$ $=\frac{294}{6}=49\,g$