MEDIUM

Earn 100

The combustion of one mole of benzee takes place at $298 K$ and $1$ atm. After combustion, ${CO}_{2}$ (g) and $H_{2} O$ (l) are produced and $3267.0 KJ$ of heat is liberated. Calculate the standard ethalpy of formation, $Δ_{f} H^{⊖}$ of benzene.

Stadard enthalpies of formation of ${CO}_{2}$ (g) and $H_{2} O$ (l) are $- 393.5 Kj {mol}^{- 1}$ and $- 285.83 KJ {mol}^{- 1}$ respectively.

Important Questions on Thermodynamics

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

Lattice enthalpy and enthalpy of solution of

NaCl

are

788 {kJmol}^{- 1}

and

4 k J m o l^{- 1}

, respectively. The hydration enthalpy of

N a C l

is:

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

The combustion of benzene

(l)

gives

{CO}_{2} (g)

and

H_{2} O (l) .

Given that heat of combustion of benzene at constant volume is

- 3263 .9 kJ {mol}^{- 1}

25 ° C;

the heat of combustion

(in kJ {mol}^{- 1})

of benzene at constant pressure will be

(R = 8 .314 {JK}^{- 1} {mol}^{- 1})

HARD

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

Choose the reaction(s) from the following options, for which the standard enthalpy of reaction is equal to the standard enthalpy of formation.

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

The elements with the highest and the lowest enthalpy of atomisation respectively, for first row transition elements are:

EASY

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

Identify the INVALID equation.

HARD

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

The enthalpies of formation of

{CO}_{(g)}, {CO}_{2 (g)}

and

N_{2} O_{(g)}

are -110,-393 and

81 kJ {mol}^{- 1}

respectively. If the enthalpy of reaction

(Δ_{r} H)

for

N_{2} O_{4 (g)} + 3 {CO}_{(g)} \to N_{2} O_{(g)} + 3 {CO}_{2 (g)}

- 778 kJ,

the enthalpy of formation of

N_{2} O_{4} (g)

{kJmol}^{- 1}

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

The heats of combustion of carbon and carbon monoxide are

- 393.5 a n d - 283.5 k J m o l^{- 1},

respectively. The heat of formation

(in kJ)

of carbon monoxide per mole is:

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

The standard enthalpy of combustion of carbon is

393.5 kJ {mol}^{- 1}

. The amount of heat released when carbon and oxygen gas produce

35.2 g

{CO}_{2}

HARD

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

The standard enthalpies of formation of ${CO}_{2} (g)$ $, H_{2} O (l)$ and glucose (s) at $2 5^{o} C$ are $- 400 kJ / mol$ , $- 300 kJ / mol$ and $- 1300 kJ / mol$ , respectively. The standard enthalpy combustion per gram of glucose at $2 5^{o} C$ is

( ${ΔH}_{f}^{0} = - 1300 kJ {mol}^{- 1}$ for Glucose)

HARD

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

For the reaction

N_{2} + 3 X_{2} \to 2 {NX}_{3}

where

X = F, Cl

(the average bond energies are

F - F = 155 kJ {mol}^{- 1}, N - F = 272 kJ {mol}^{- 1}, Cl - Cl = 242 kJ {mol}^{- 1}, N - Cl = 200 kJ {mol}^{- 1}

and

N \equiv N = 941 kJ {mol}^{- 1}

), the heats of reaction of

{NF}_{3}

and

{NCl}_{3}

kJ {mol}^{- 1},

respectively, are closest to

HARD

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

For one mole of NaCl(s) the lattice enthalpy is

${Na}_{(s)} + \frac{1}{2} {Cl}_{2} (g) \overset{+ 108.4 kJ / mol}{⟶} {Na}_{(s)} + \frac{1}{2} {Cl}_{2} (g) \overset{+ 495.6 kJ / mol}{⟶} {Na}_{(g)}^{+} + \frac{1}{2} {Cl}_{2} (g) \overset{121 kJ / mol}{⟶}$

${Na}_{(g)}^{+} + Cl (g) \overset{- 348.6 kJ / mol}{⟶} {Na}_{(g)}^{+} + {Cl}_{(g)}^{-} \overset{{ΔH}^{0} altice}{⟶} Nacl$ (solid) $\underset{- 411.2 kJ / mol}{\leftarrow} {Na}_{(s)} + \frac{1}{2} {Cl}_{2} (g)$

EASY

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

The heat of combustion of carbon to

C O_{2}

- 393.5 kJ / mol

. The heat released upon the formation of

35.2 g

C O_{2}

from carbon and oxygen gas is

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

The average $S - F$ bond energy in $kJ {mol}^{- 1}$ of ${SF}_{6}$ is _. (Rounded off to the nearest integer)

[Given : The values of standard enthalpy of formation of ${SF}_{6} (g), S (g)$ and $F (g)$ are $- 1100, 275$ and $80 kJ {mol}^{- 1}$ respectively.]

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

Enthalpy of combustion of methane and ethane are

- 210 k cal / mol

and

- 368 k cal / mol

respectively. The enthalpy of combustion of decane is

EASY

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

The standard enthalpies of formation of ${Al}_{2} O_{3}$ and $CaO$ are $- 1675 kJ {mol}^{- 1}$ and $- 635 kJ {mol}^{- 1}$ respectively.

For the reaction

$3 CaO + 2 Al \to 3 Ca + {Al}_{2} O_{3}$ the standard reaction enthalpy $Δ_{r} H^{0} =$ ________ $kJ .$

(Round off to the Nearest Integer).

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

What will be the enthalpy of formation of toluene considering the data given?
Bond energies of

C - C = 79 kcal, C = C = 135 kcal,

C - H = 102 kcal,

heat of atomisation of

C = 156.8 kcal

and heat of atomisation of

H = 49.5 kcal

EASY

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

Given that bond energies of

H - H

and

Cl - Cl

are

430 kJ {mol}^{- 1}

and

240 kJ {mol}^{- 1}

respectively and

{ΔH}_{f}

for

HCl

- 90 kJ {mol}^{- 1}

. The bond energy of

HCl

MEDIUM

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

The standard enthalpy of formation of

{NH}_{3}

- 46.0 kJ / mol

. If bond enthalpy of

H_{2}

- 436 kJ / mol

and that of

N_{2}

- 712 kJ / mol

, the average bond enthalpy of

N - H

bond in

{NH}_{3}

is :

HARD

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

The heat of atomization of methane and ethane are

360 kJ {mol}^{- 1}

and

620 kJ {mol}^{- 1}

, respectively. The longest wavelength of light capable of breaking the

C - C

bond is (Avogadro's number

= 6.023 \times 10^{23}, h = 6.62 \times 10^{- 34} J s

)

EASY

Chemistry>Physical Chemistry>Thermodynamics>Enthalpy Change of a Reaction- Reaction Enthalpy

The enthalpy change on freezing of

1 mol

of water at

5 ° C

to ice at

- 5 ° C

is:

(Given

Δ_{fus} H = 6 kJ {mol}^{- 1}

0 ° C,

C_{p} (H_{2} O, l) = 75 .3 J {mol}^{- 1} K^{- 1}

C_{p} (H_{2} O, s) = 36 .8 J {mol}^{- 1} K^{- 1}

)

Important Questions on Thermodynamics

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