QJEEM20Ch9b35: JEE Main 2020 Chemistry - Class 12 JEEM20Ch9b35 Solution: An acidic solution of dichromate is electrolyzed for 8 minutes…

Question

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An acidic solution of dichromate is electrolyzed for 8 minutes using 2A current. As per the following equation
Cr₂O₇^2- + 14H⁺ + 6e^–

\to

2Cr³⁺ + 7H₂O
The amount of Cr³⁺ obtained was 0.104 g. The efficiency of the process(in%) is (Take : F = 96000 C, At. mass of chromium = 52) ______.

Accepted Answer

Cr₂O₇^2- + 14H⁺ + 6e^–

\to

2Cr³⁺ + 7H₂O

I = 2 A, t = 8 min

From 1^st law of faraday,

w_Cr⁺³ = z

\times

i

\times

t

\Rightarrow

w_Cr⁺³ =

\frac{52}{96000 \times 3} \times 2 \times 8 \times 60

=

\frac{52}{300}

Mass of Cr³⁺ ions actually obtained = 0.104 gm

% efficiency =

Actual obtained Amt

Theo. obtained Amt

\times

100

=

\frac{0.104}{\frac{52}{300}}

\times

100

= 60 %

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