1
JEE Main 2020 (Online) 3rd September Evening Slot
Numerical
+4
-0
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) ______.
2
JEE Main 2020 (Online) 3rd September Morning Slot
Numerical
+4
-0
The photoelectric current from Na (Work function, w0 = 2.3 eV) is stopped by the output voltage of the cell
Pt(s) | H2 (g, 1 Bar) | HCl (aq., pH =1) | AgCl(s) | Ag(s).
The pH of aq. HCl required to stop the photoelectric current form K(w0 = 2.25 eV), all other conditions remaining the same, is _______ $$\times$$ 10-2 (to the nearest integer).

Given, 2.303$${{RT} \over F}$$ = 0.06 V;
$$E_{AgCl|Ag|C{l^ - }}^0$$ = 0.22 V
3
JEE Main 2020 (Online) 2nd September Evening Slot
Numerical
+4
-0
For the disproportionation reaction
2Cu+(aq) ⇌ Cu(s) + Cu2+(aq) at 298 K. ln K
(where K is the equilibrium constant) is
___________ × 10–1.
Given :
($$E_{C{u^{2 + }}/C{u^ + }}^0 = 0.16V$$
$$E_{C{u^ + }/Cu}^0 = 0.52V$$
$${{RT} \over F} = 0.025$$)
4
JEE Main 2020 (Online) 2nd September Morning Slot
Numerical
+4
-0
The Gibbs change (in J) for the given reaction at
[Cu2+] = [Sn2+] = 1 M and 298K is :

Cu(s) + Sn2+(aq.) $$\to$$ Cu2+(aq.) + Sn(s);

($$E_{S{n^{2 + }}|Sn}^0 = - 0.16\,V$$,
$$E_{C{u^{2 + }}|Cu}^0 = 0.34\,V$$)
Take F = 96500 C mol–1)
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