JEE MAIN - Chemistry (2020 - 3rd September Evening Slot - No. 21)
An acidic solution of dichromate is electrolyzed
for 8 minutes using 2A current. As per the
following equation
Cr2O72- + 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) ______.
Cr2O72- + 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) ______.
Answer
60
Explanation
Cr2O72-
+ 14H+ + 6e– $$ \to $$ 2Cr3+ + 7H2O
I = 2 A, t = 8 min
From 1st law of faraday,
wCr+3 = z $$ \times $$ i $$ \times $$ t
$$ \Rightarrow $$ wCr+3 = $${{52} \over {96000 \times 3}} \times 2 \times 8 \times 60$$
= $${{52} \over {300}}$$
Mass of Cr3+ ions actually obtained = 0.104 gm
% efficiency =
= $${{0.104} \over {{{52} \over {300}}}}$$ $$ \times $$ 100
= 60 %
I = 2 A, t = 8 min
From 1st law of faraday,
wCr+3 = z $$ \times $$ i $$ \times $$ t
$$ \Rightarrow $$ wCr+3 = $${{52} \over {96000 \times 3}} \times 2 \times 8 \times 60$$
= $${{52} \over {300}}$$
Mass of Cr3+ ions actually obtained = 0.104 gm
% efficiency =
Actual obtained Amt
Theo. obtained Amt
$$ \times $$ 100
= $${{0.104} \over {{{52} \over {300}}}}$$ $$ \times $$ 100
= 60 %
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