An acidic solution of dichromate is electroly | vedclass

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Question

(A) Total charge passed $Q = I 	imes t = 2 \ A 	imes (8 	imes 60) \ s = 960 \ C$. Moles of electrons passed $= \frac{Q}{F} = \frac{960}{96000} = 0.

Vedclass · Accepted Answer

$60$

Vedclass · Answer

(A) Total charge passed $Q = I 	imes t = 2 \ A 	imes (8 	imes 60) \ s = 960 \ C$. Moles of electrons passed $= \frac{Q}{F} = \frac{960}{96000} = 0.01 \ mol$. According to the reaction $Cr_{2}O_{7}^{2-} + 14H^{+} + 6e^{-} ightarrow 2Cr^{3+} + 7H_{2}O$,$6 \ mol$ of $e^{-}$ produce $2 \ mol$ of $Cr^{3+}$. Theoretical moles of $Cr^{3+} = \frac{2}{6} 	imes 0.01 = 0.00333 \ mol$. Theoretical mass of $Cr^{3+} = 0.00333 \ mol 	imes 52 \ g/mol = 0.1733 \ g$. Efficiency $(\%) = \frac{	ext{Actual mass}}{	ext{Theoretical mass}} 	imes 100 = \frac{0.104}{0.1733} 	imes 100 \approx 60 \%$.

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