1
JEE Main 2021 (Online) 24th February Evening Shift
Numerical
+4
-1
The magnitude of the change in oxidising power of the $$MnO_4^ - /M{n^{2 + }}$$ couple is x $$\times$$ 10$$-$$4 V, if the H+ concentration is decreased from 1M to 10$$-$$4 M at 25$$^\circ$$C. (Assume concentration of $$MnO_4^ -$$ and $$M{n^{2 + }}$$ to be same on change in H+ concentration). The value of x is ___________. $$\left[ {Given\,:{{2.303RT} \over F} = 0.059} \right]$$
2
JEE Main 2020 (Online) 6th September Morning Slot
Numerical
+4
-0
Potassium chlorate is prepared by the electrolysis of KCl in basic solution

6OH- + Cl- $$\to$$ ClO3- + 3H2O + 6e-

If only 60% of the current is utilized in the reaction, the time (rounded to the nearest hour) required to produce 10 g of KClO3 using a current of 2 A is_________.

(Given : F = 96,500 C mol–1; molar mass of KCIO3 = 122 g mol–1)
3
JEE Main 2020 (Online) 5th September Morning Slot
Numerical
+4
-0
An oxidation-reduction reaction in which
3 electrons are transferred has a $$\Delta$$Gº of 17.37 kJ mol–1 at
25 oC. The value of Eo
cell (in V) is ______ × 10–2.
(1 F = 96,500 C mol–1)
4
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) ______.