$Cr _{2} O _{7}^{2-}+14 H ^{+}+6 e ^{-} \rightarrow 2 Cr ^{3+}+7 H _{2} O$
The amount of $Cr ^{3+}$ obtained was $0.104\, g$. The
efficiency of the process(in\%) is
(Take : $F =96000\, C$, At. mass of chromium $=52$ )
Using stoichiometry; theoritically
$\frac{ n _{ e ^{\ominus}} used }{6}=$$\frac{ n _{ cr ^{+3}} \text {produced }}{2}$
$\Rightarrow n _{ cr ^{+3}}$ produced $=\frac{2}{6} \times \frac{8 \times 60 \times 2}{96000}$
$=\frac{0.02}{6}$
$\Rightarrow wt _{ cr ^{+3}}$ theoritically produced
$=\left(\frac{0.02}{6} \times 52\right) g$
$\Rightarrow \%$ efficiency $=\frac{0.104 g }{\left(\frac{0.02 \times 52}{6}\right) g } \times 100$
$=60 \%$
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[Assume $100 \%$ ionisation of the complex and $CaCl _{2},$ coordination number of $Cr$ as $6,$ and that all $NH _{3}$ molecules are present inside the coordination sphere $]$
Reason : $sp$ hybridised carbon atoms of acetylene are considerably electronegative.
| Expt. No. | $(A)$ | $(B)$ | Initial Rate |
| $1$ | $0.012$ | $0.035$ | $0.10$ |
| $2$ | $0.024$ | $0.070$ | $0.80$ |
| $3$ |
$0.024$ |
$0.035$ | $0.10$ |
| $4$ | $0.012$ | $0.070$ | $0.80$ |