Question

Select the correct statements among following:

• A. In the dichromate dianion, six equivalent $Cr-O$ bonds and one $Cr-O-Cr$ bonds are present
• B. One mole of $S{n}^{2+}$ will reduce $\frac{1}{3}$ moles of $K_{2}C{r}_2{O}_7$ in acidic condition
• C. One mole of $S{n}^{2+}$ will reduce $\frac{2}{3}$ moles of $K_{2}C{r}_2{O}_7$ in acidic condition
• D. In the dichromate dianion, six equivalent $Cr-O$ bonds and one $Cr-Cr$ bonds are present

Answer 1

Answer: (A), (B)

One mole of $S{n}^{2+}$ will reduce $\frac{1}{3}$ moles of $K_{2}C{r}_2{O}_7$ in acidic condition

Structure of dichromate dianion can be given as:


Hence, in the dichromate dianion, six equivalent $Cr-O$ bonds and one $Cr-O-Cr$ bonds are present
In acidic condition, acidified potassium dichromate oxidises tin(II) to tin(IV). The balanced chemical equation is:
$3S{n}^{2+}+C{r}_2{O}_7^{2-}+14H^{+}\to 3S{n}^{4+}+2C{r}^{3+}+7H_{2}O$
Thus, one mole of $S{n}^{2+}$ will be reduced by $\frac{1}{3}$ moles of $C{r}_2{O}_7^{2-}$.