Enthalpy of polymerisation of ethylene, as represented by the reaction, nCH 2 = CH 2 ⟶ - CH 2 - CH 2 - n is - 100 kJ per mole of ethylene. Given bond enthalpy of C = C bond is 600 kJ mol - 1 , determine enthalpy of C - C bond (in kJ mol ).

nCH 2 = CH 2 ⟶ - CH 2 - CH 2 - n ΔH = - 100 KJ / mole Double bond of ethylene converted to two single bonds. ΔH = - 100 = B . E . C = C - 2 B . E . C - C ⇒ - 100 = 600 - 2 × B . E . c - c ⇒ B . E . C - C = 350 KJ / mole .

For the hypothetical reaction: A 2 g + B 2 g ⇌ 2 AB g If Δ r G o - and Δ r S o - are 20 kJ / mol and - 20 JK - 1 mol - 1 , respectively at 200 K . Δ r C p is 20 JK - 1 mol - 1 then determine Δ r H ° at 400 K .

From the equation: ΔG 200 0 = ΔH 200 0 - TΔS 200 0 ΔH 200 0 = 20 + - 20 × 200 = 16 kJ / mol Now, by Kirchoff's equation: ΔH T 2 0 = ΔH T 1 0 + ΔC p T 2 - T 1 ΔH 400 0 = ΔH 200 0 + 20 × 200 1000 kJ / mol = 16 + 4 = 20 kJ / mol .

MEDIUM

KVPY Aptitude Test - Stream SA

IMPORTANT

Earn 100

From the following data, determine the enthalpy change for the sublimation of ice at $223 K$ . [Mean heat capacity of ice $= 2 {JK}^{- 1} {gm}^{- 1}$ , mean heat capacity of $H_{2} O (l) = 4.2 {JK}^{- 1} {gm}^{- 1}$ , mean heat capacity of $H_{2} O (g) = 1.85 {JK}^{- 1} {gm}^{- 1}$ , enthalpy of fusion of ice at $0 ° C = 334 J {gm}^{- 1}$ , enthalpy of evaporation of water at $100 ° C = 2255 J {gm}^{- 1}$ ]

Important Questions on Thermodynamics & Thermochemistry

MEDIUM

KVPY Aptitude Test - Stream SA

IMPORTANT

Practice Book for KVPY Aptitude Test - Stream SA Chemistry>Chapter 5 - Thermodynamics & Thermochemistry>EXERCISE>Q 43

The heat of formation of

C_{2} H_{5} OH (l)

- 66 kcal / mole

. The heat of combustion of

{CH}_{3} {OCH}_{3} (g)

- 348 kcal / mole . ∆ H_{f}

for

H_{2} O

and

{CO}_{2}

are

- 68 kcal / mole

and

- 94 kcal / mole

respectively. Then determine the

ΔH

for the isomerisation reaction

C_{2} H_{5} OH (l) ⟶ {CH}_{3} {OCH}_{3} (g)

, and

ΔE

for the same are at

T = 25 ° C

MEDIUM

KVPY Aptitude Test - Stream SA

IMPORTANT

Practice Book for KVPY Aptitude Test - Stream SA Chemistry>Chapter 5 - Thermodynamics & Thermochemistry>EXERCISE>Q 44

In the reaction,

{AB}_{2} (l) + 3 X_{2} (g) ⇌ {AX}_{2} (g) + 2 {BX}_{2} (g) ΔH = - 270 kcal per mol

{AB}_{2} (l)

, the enthalpies of formation of

{AX}_{2} (g) & {BX}_{2} (g)

are in the ratio of

4 : 3

and have opposite sign. Determine the value of

{ΔH}_{f}^{0} ({AB}_{2} (l)) = + 30 Kcal / mole

MEDIUM

KVPY Aptitude Test - Stream SA

IMPORTANT

Practice Book for KVPY Aptitude Test - Stream SA Chemistry>Chapter 5 - Thermodynamics & Thermochemistry>EXERCISE>Q 45

AB, A_{2}

and

B_{2}

are diatomic molecules. If the bond enthalpies of

A_{2}, AB & B_{2}

are in the ratio

1 : 1 : 0.5

and enthalpy of formation of

AB

from

A_{2}

and

B_{2}

- 100 kJ / {mol}^{- 1}

. What is the bond enthalpy of

A_{2}

MEDIUM

KVPY Aptitude Test - Stream SA

IMPORTANT

Practice Book for KVPY Aptitude Test - Stream SA Chemistry>Chapter 5 - Thermodynamics & Thermochemistry>EXERCISE>Q 46

When a certain amount of ethylene was combusted,

6226 kJ

heat was evolved. If heat of combustion of ethylene is

1411 kJ

, determine the volume of

O_{2}

(at

NTP

) that entered into the reaction.

MEDIUM

KVPY Aptitude Test - Stream SA

IMPORTANT

Practice Book for KVPY Aptitude Test - Stream SA Chemistry>Chapter 5 - Thermodynamics & Thermochemistry>EXERCISE>Q 47

Given the following reactions:

I: $N_{2} (g) + 2 O_{2} (g) ⟶ 2 {NO}_{2} (g), {ΔH}_{I} = 16.18 kcal$

II: $N_{2} (g) + 2 O_{2} (g) ⟶ N_{2} O_{4} (g), {ΔH}_{II} = 2.31 kcal$

Which amongst ${NO}_{2} (g)$ and $N_{2} O_{4} (g)$ is more stable?

MEDIUM

KVPY Aptitude Test - Stream SA

IMPORTANT

Practice Book for KVPY Aptitude Test - Stream SA Chemistry>Chapter 5 - Thermodynamics & Thermochemistry>EXERCISE>Q 48

Enthalpy of polymerisation of ethylene, as represented by the reaction,

{nCH}_{2} = {CH}_{2} ⟶ {(- {CH}_{2} - {CH}_{2} -)}_{n}

- 100 kJ

per mole of ethylene. Given bond enthalpy of

C = C

bond is

600 kJ {mol}^{- 1}

, determine enthalpy of

C - C

bond (in

kJ mol

MEDIUM

KVPY Aptitude Test - Stream SA

IMPORTANT

Practice Book for KVPY Aptitude Test - Stream SA Chemistry>Chapter 5 - Thermodynamics & Thermochemistry>EXERCISE>Q 49

Substance $A_{2} B (g)$ can undergo decomposition to form two sets of products:

Question Image

If the molar ratio of $A_{2} (g)$ to $A (g)$ is $5 : 3$ in a set of product gases, determine then the energy involved in the decomposition of $1$ mole of $A_{2} B$ .

MEDIUM

KVPY Aptitude Test - Stream SA

IMPORTANT

Practice Book for KVPY Aptitude Test - Stream SA Chemistry>Chapter 5 - Thermodynamics & Thermochemistry>EXERCISE>Q 50

For the hypothetical reaction:

$A_{2} (g) + B_{2} (g) ⇌ 2 AB (g)$

If $Δ_{r} G^{\underline{o}}$ and $Δ_{r} S^{\underline{o}}$ are $20 kJ / mol$ and $- 20 {JK}^{- 1} {mol}^{- 1}$ , respectively at $200 K . Δ_{r} C_{p}$ is $20 {JK}^{- 1} {mol}^{- 1}$ then determine $Δ_{r} H °$ at $400 K$ .

Important Questions on Thermodynamics & Thermochemistry

Learn and Prepare for any exam you want !