Pradeep's Chemistry Vol 1>Chapter 7 - Thermodynamics>Competition Focus>Q 60

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Enthalpy change of ${CH}_{4} + \frac{1}{2} O_{2} \to {CH}_{3} OH$ is negative. If enthalpy of combustion of ${CH}_{4}$ and ${CH}_{3} OH$ are $x$ and $y$ respectively, then which relation is correct?

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Important Questions on Thermodynamics

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11th CBSE

IMPORTANT

Pradeep's Chemistry Vol 1>Chapter 7 - Thermodynamics>Competition Focus>Q 61

The standard heat of formation of

{NO}_{2} (g)

and

N_{2} O_{4} (g)

are

8.0

and

2 \cdot 0 kcal {mol}^{- 1}

respectively. The heat of dimerization of

{NO}_{2}

in

kcal

is

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Pradeep's Chemistry Vol 1>Chapter 7 - Thermodynamics>Competition Focus>Q 62

Consider the reaction

$4 {NO}_{2} (g) + O_{2} (g) \to 2 N_{2} O_{5} (g), ∆_{r} H = - 111 kJ$

If $N_{2} O_{5} (s)$ is formed instead of $N_{2} O_{5} (g)$ in the above reaction, the $∆_{r} H$ value will be (given, $∆ H$ of sublimation for $N_{2} O_{5}$ is $54 kJ {mol}^{- 1}$ )

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Pradeep's Chemistry Vol 1>Chapter 7 - Thermodynamics>Competition Focus>Q 63

Consider the following processes :

Question Image

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Pradeep's Chemistry Vol 1>Chapter 7 - Thermodynamics>Competition Focus>Q 64

The standard enthalpies of formation of

{CO}_{2} (g), H_{2} O (l) and glucose (s)

at

25 ° C

are

- 400 kJ / mol, - 300 kJ / mol and - 1300 kJ / mol

respectively. The standard enthalpy of combustion per gram of glucose at

25 ° C

is-

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Pradeep's Chemistry Vol 1>Chapter 7 - Thermodynamics>Competition Focus>Q 65

The heats of combustion of carbon and carbon monoxide are

- 393.5

and

- 283 \cdot 5 kJ {mol}^{- 1}

respectively. The heat of formation (in

kJ

) of carbon monoxide per mole is

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Pradeep's Chemistry Vol 1>Chapter 7 - Thermodynamics>Competition Focus>Q 66

Given-

C (graphite) + O_{2} (g) \to {CO}_{2} (g), ∆_{r} H º = - 393 \cdot 5 kJ {mol}^{- 1} . . . (i) H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (l), ∆_{r} H º = - 285 \cdot 8 kJ {mol}^{- 1} . . . (ii) {CO}_{2} (g) + 2 H_{2} O (I) \to {CH}_{4} (g) + 2 O_{2} (g), ∆_{r} H º = + 890.3 kJ {mol}^{- 1} . . . (iii)

Based on the above thermochemical equations, the value of

$∆_{r} H º$ at $298 K$ for the reaction $C (graphite)$ + $2 H_{2} (g) \to {CH}_{4} (g)$ will be

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Pradeep's Chemistry Vol 1>Chapter 7 - Thermodynamics>Competition Focus>Q 67

The bond energy of an

O - H

bond is

109 kcal / mol

. When a mole of water is formed, then

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Pradeep's Chemistry Vol 1>Chapter 7 - Thermodynamics>Competition Focus>Q 68

If the bond dissociation energies of

XY, X_{2} & Y_{2}

(all diatomic molecules) are in the ratio

1 : 1 : 0.5

and

∆ H_{f}

for the formation of

XY

is

- 200 kJ {mol}^{- 1}

, the bond dissociation energy of

X_{2}

will be