1
JEE Main 2022 (Online) 24th June Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

At 25$$^\circ$$C and 1 atm pressure, the enthalpies of combustion are as given below :

Substance $${H_2}$$ C (graphite) $${C_2}{H_6}(g)$$
$${{{\Delta _c}{H^\Theta }} \over {kJ\,mo{l^{ - 1}}}}$$ $$ - 286.0$$ $$ - 394.0$$ $$ - 1560.0$$

The enthalpy of formation of ethane is

A
+54.0 kJ mol$$-$$1
B
$$-$$68.0 kJ mol$$-$$1
C
$$-$$86.0 kJ mol$$-$$1
D
+97.0 kJ mol$$-$$1
2
JEE Main 2021 (Online) 31st August Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
The incorrect expression among the following is :
A
$${{\Delta {G_{System}}} \over {\Delta {S_{Total}}}} = - T$$ (at constant P)
B
$$K = {{\Delta H^\circ - T\Delta S^\circ } \over {RT}}$$
C
$$K = {e^{ - \Delta G^\circ /RT}}$$
D
For isothermal process $${w_{reversible}} = - nRT\ln {{{V_f}} \over {{V_i}}}$$
3
JEE Main 2021 (Online) 17th March Evening Shift
MCQ (Single Correct Answer)
+4
-1
During which of the following processes, does entropy decrease?

(A) Freezing of water to ice at 0$$^\circ$$C

(B) Freezing of water to ice at $$-$$10$$^\circ$$C

(C) N2(g) + 3H2(g) $$ \to $$ 2NH3(g)

(D) Adsorption of CO(g) on lead surface.

(E) Dissolution of NaCl in water

Choose the correct answer from the options given below :
A
(A), (C) and (E) only
B
(B) and (C) only
C
(A), (B), (C) and (D) only
D
(A) and (E) only
4
JEE Main 2020 (Online) 6th September Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
For a reaction,
4M(s) + nO2(g) $$ \to $$ 2M2On(s)
the free energy change is plotted as a function of temperature. The temperature below which the oxide is stable could be inferred from the plot as the point at which :
A
the free energy change shows a change from negative to positive value
B
the slope changes from positive to negative
C
the slope changes from negative to positive
D
the slope changes from positive to zero
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