1
MCQ (Single Correct Answer)

AIPMT 2000

2Zn + O2 $$ \to $$ 2ZnO;  $$\Delta $$Go = $$-$$ 616 J
2Zn + S2 $$ \to $$ 2ZnS;  $$\Delta $$Go = $$-$$ 293 J
S2 + 2O2 $$ \to $$ 2SO2;   $$\Delta $$Go = $$-$$408 J
$$\Delta $$Go for the following reaction
2ZnS + 3O2 $$ \to $$  2ZnO + 2SO2 is
A
$$-$$ 731 J
B
$$-$$ 1317 J
C
$$-$$ 501 J
D
+ 731 J

Explanation

2Zn + O2 $$ \to $$ 2ZnO;  $$\Delta $$Go = $$-$$ 616 J ....(1)
2ZnS $$ \to $$ 2Zn + O2;  $$\Delta $$Go = $$+$$ 293 J.....(2)
S2 + 2O2 $$ \to $$ 2SO2;   $$\Delta $$Go = $$-$$408 J .....(3)

$$\Delta $$Go for the reaction can be obtained by adding (1), (2) and (3)

$$ \therefore $$ $$\Delta $$Go = 293 - 616 - 408 = -731 J
2
MCQ (Single Correct Answer)

AIPMT 2000

Cell reaction is spontaneous when
A
$$\Delta $$Go is negative
B
$$\Delta $$Go is positive
C
$$\Delta $$Eored is positive
D
$$\Delta $$Eored is negative

Explanation

For spontaneous reaction $$\Delta $$Go = – ve and

Eocell = + ve

as $$\Delta $$Go = – nFEocell

where, n = number of electrons taking part

Eo = emf of cell

F = Faraday constant

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