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CBSE

Subject

Chemistry

NEET Chemistry : Thermodynamics

Multiple Choice Questions

41.

The entropy values (in JK^-1mol^-1) of H₂(g) = 130.6, Cl₂(g) = 223.0 and HCl (g) = 186. 7 at 298 K and 1 atm pressure. Then entropy change for the reaction :

H₂ ( g)+ Cl₂(g) $\to$ 2HCl (g) is:

+540.3
+727.3
-166.9
+19.8

42.

The absolute enthalpy of neutralisation of the reaction

MgO(s) + 2HCl(aq) $\to$ MgCl₂(aq) + H₂O(l)

will be

less than - 57.33 kJ mol^-1
- 57.33 kJ mol^-1
greater than-- 57.33 kJ mol^-1
57.33 kJ mol^-1

43.

The entropy will be positive in which of the following reaction change.

H₂(g) + I₂ (g) $⇋$ 2HI (g)
HCl(g) + NH₃ (g) $⇋$ N₂O(g) + 2H₂O(g)
NH₄NO₃(s) $⇋$ N₂O(g) + 2H₂O(g)
MgO(s) + H₂(g) $⇋$ Mg(s) + H₂O(l)

44.

Which of the following pairs of a chemical reaction is certain to result in a spontaneous reaction?

Exothermic and decreasing disorder
Endothermic and increasing disorder
Exothermic and increasing disorder
Endothermic and decreasing disorder

45.

Consider the respective enthalpy for the following reactions:

$(I) {NH}_{3} (g) + 3 {Cl}_{2} (g) ⇌ {NCl}_{3} (g) + 3 HCl (g); - {ΔH}_{1} (II) N_{2} (g) + 3 H_{2} (g) ⇌ 2 {NH}_{3} (g); - {ΔH}_{2} (III) H_{2} (g) + {Cl}_{2} (g) ⇌ 2 HCl (g); {ΔH}_{3}$

$The enthalpy of formation of {NCl}_{3} (g) in terms of {ΔH}_{1}, {ΔH}_{2,} {ΔH}_{3} is :$

${ΔH}_{f} = - {ΔH}_{1} + \frac{{ΔH}_{2}}{2} - \frac{3}{2} {ΔH}_{3}$
${ΔH}_{f} = {ΔH}_{1} + \frac{{ΔH}_{2}}{2} - \frac{3}{2} {ΔH}_{3}$
${ΔH}_{f} = - {ΔH}_{1} - \frac{{ΔH}_{2}}{2} - \frac{3}{2} {ΔH}_{3}$
None of the above

46.

Which of the following have highest electron affinity?

47.

The change in entropy for the fusion of 1 mole of ice is [mp of ice = 273 K, molar enthalpy of fusion for ice= 6.0 kJ mol^-1]

11.73 JK^-1 mol^-1
18.84 JK^-1 mol^-¹
21.97 JK^-1 mol^-1
24.47 JK^-1 mol^-1

48.

The enthalpy of combustion at 25°C of H₂, cyclohexane (C₆H₁₂) and cyclohexene (C₆H₁₀) are -241, -3920 and -3800 kJ/mol respectively. The heat of hydrogenation of cyclohexene is :

-121 kJ/mol
+121 kJ/mol
-242 kJ/mol
+242 kJ/mol

49.

A reaction occurs spontaneously if

T $∆$ S < $∆$ H and both $∆$ H and $∆$ S are +ve
T $∆$ S > $∆$ H and both $∆$ H and $∆$ S are +ve
T $∆$ S = $∆$ H and both $∆$ H and $∆$ S are +ve
T $∆$ S > $∆$ H and $∆$ H is +ve and $∆$ S is - ve

50.

C_(dia) + O₂ $\to$ CO₂; $∆ H$ = - 395.4 kJ/ mol

C_(gr) + O₂ $\to$ CO₂; $∆$ H = - 393.5 kJ/ mol

C_(gr) $\to$ C_(dia); $∆$ H = ?

-3.8
-1.9
+3.8
+1.9

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