For the reaction, S (rhombic) + O 2 → SO 2 ΔH = - 298 kJ mol - 1 at 25 ° C and 1 atm . Therefore, Δ E for the reaction should be

- 298 + 8 . 314 × 298 kJ mol - 1

- 298 - 8 . 314 × 298 kJ mol - 1

- 298 - 2 × 8 . 314 × 298 kJ mol - 1

The reaction in which ΔH > ΔU is

CaCO 3 ( s ) ⟶ CaO ( s ) + CO 2 ( g )

N 2 ( s ) + 3 H 2 ( g ) ⟶ 2 NH 3 ( g )

CH 4 ( g ) + 2 O 2 ( g ) ⟶ CO 2 ( g ) + 2 H 2 O ( l )

N 2 ( g ) + O 2 ( g ) ⟶ 2 NO ( g )

EASY

Earn 100

The heat change at constant volume for the decomposition of silver oxide is found to be $80.25 kJ$ . The heat change at constant pressure will be______.

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Important Questions on Chemical Thermodynamics

HARD

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

Given:

C (graphite) + O_{2} (g) \to {CO}_{2} (g); Δ_{r} H^{o} = - 393 .5 kJ {mol}^{- 1}

H_{2} (g) + \frac{1}{2} O_{2} (g) \to H_{2} O (l); Δ_{r} H^{o} = - 285 .8 kJ {mol}^{- 1}

{CO}_{2} (g) + 2 H_{2} O (l) \to {CH}_{4} (g) + 2 O_{2} (g); Δ_{r} H^{o} = + 890 .3 kJ {mol}^{- 1}

Based on the above thermochemical equations, the value of

Δ_{r} H^{o}

298 K

for the reaction

C (graphite) + 2 H_{2} (g) \to {CH}_{4} (g)

will be:

MEDIUM

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

For the reaction $H_{2} F_{2} (g) \to H_{2} (g) + F_{2} (g)$

$ΔU = - 59.6 kJ {mol}^{- 1}$ at $27 ° C$

The enthalpy change for the above reaction is $(-)$ ____ ${kJmol}^{- 1}$ (nearest integer)

(Given : $R = 8.314 {JK}^{- 1} {mol}^{- 1}$ ) .

EASY

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

Consider the reaction,

N_{2} + 3 H_{2} \to 2 {NH}_{3}

, carried out at a constant temperature and pressure. If

ΔH

and

ΔU

are the enthalpy and internal energy changes for the reaction, which of the following expressions is true?

HARD

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

For complete combustion of ethanol,

C_{2} H_{5} OH (l) + 3 O_{2} (g) \to 2 {CO}_{2} (g) + 3 H_{2} O (l)

,
the amount of heat produced as measured in bomb calorimeter, is

{1364.47 kJ mol}^{-1}

25 ℃

. Assuming ideality the Enthalpy of combustion,

Δ_{c} H

, for the reaction will be:

(R = {8.314 kJ mol}^{-1})

EASY

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

For the reaction,

S_{(rhombic)} + O_{2} \to {SO}_{2}

ΔH = - 298 kJ {mol}^{- 1}

25 ° C

and

1 atm

. Therefore,

Δ E

for the reaction should be

MEDIUM

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

Given that the bond energies of:

N \equiv N is 946 kJ {mol}^{- 1}, H - H is 435 kJ {mol}^{- 1}, N - N is 159 kJ {mol}^{- 1},

and

N - H is 389 kJ {mol}^{- 1}

, the heat of formation of hydrazine in the gas phase in

kJ {mol}^{- 1}

is:

MEDIUM

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

Which one of the following is the correct relation between

C_{P}

and

C_{V}

for one mole of an ideal gas? (

R

is molar gas constant)

MEDIUM

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

For the reaction

$N_{2} O_{4} (g) ⟶ 2 {NO}_{2} (g)$

MEDIUM

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

The reaction of cyanamide,

{NH}_{2} {CN}_{(s)}

with oxygen was run in a bomb calorimeter and

ΔU

was found to be

- 742.24 kJ {mol}^{- 1}

. The magnitude of

{ΔH}_{298}

for the reaction

{NH}_{2} {CN}_{(s)} + \frac{3}{2} O_{2 (g)} \to N_{2 (g)} + O_{2 (g)} + H_{2} O_{(l)}

kJ

. (Rounded off to the nearest integer) [Assume ideal gases and

R = 8.314 J {mol}^{- 1} K^{- 1}

]

MEDIUM

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

For water

Δ_{vap} H = 41 kJ {mol}^{- 1}

373 K

and 1 bar pressure. Assuming that water vapour is an ideal gas that occupies a much larger volume than liquid water, the internal energy change during evaporation of water is

({kJmol}^{- 1})

:
[ Use

: R = 8.3 J {mol}^{- 1} K^{- 1}]

EASY

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

The difference between

∆ H

and

∆ U

(∆ H - ∆ U)

, when the combustion of one mole of heptane

(l)

is carried out at a temperature

T

, is equal to:

EASY

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

The reaction in which

ΔH > ΔU

HARD

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

Tin is obtained from cassiterite by reduction with coke. Use the data given below to determine the minimum temperature (in $K$ ) at which the reduction of cassiterite by coke would take place.

$298 K : Δ_{f} H^{0} ({SnO}_{2} (s)) = - 581.0 kJ {mol}^{- 1}, Δ_{f} H^{0} ({CO}_{2} (g)) = - 394.0 kJ {mol}^{- 1}$

$S^{0} ({SnO}_{2} (s)) = 56.0 {JK}^{- 1} {mol}^{- 1}, S^{0} (Sn (s)) = 52.0 {JK}^{- 1} {mol}^{- 1}$

$S^{0} (C (s)) = 6.0 {JK}^{- 1} {mol}^{- 1}, S^{0} ({CO}_{2} (g)) = 210.0 {JK}^{- 1} {mol}^{- 1}$

Assume that the enthalpies and the entropies are temperature independent.

EASY

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

For a reaction,

A (g) \to A (l); ΔH = - 3 RT .

The correct statement for the reaction is

MEDIUM

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

At standard conditions, if the change in the enthalpy for the following reaction is $- 109 {kJmol}^{- 1}$

$H_{2 (g)} + {Br}_{2 (g)} \to 2 {HBr}_{(g)}$

Given that bond energy of $H_{2}$ and ${Br}_{2}$ is $435 {kJmol}^{- 1}$ and $192 {kJmol}^{- 1}$ , respectively, what is the bond energy (in $kJ {mol}^{- 1}$ ) of $HBr ?$

MEDIUM

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

When $0.8 g$ of glucose, $C_{6} H_{12} O_{6}$ , was burnt in a bomb calorimeter, according to the following equation, the temperature raise is found to be $2 K$ at $1 atm$ .

$C_{6} H_{12} O_{6 (s)} + 6 O_{2 (g)} ⟶ 6 {CO}_{2 (g)} + 6 H_{2} O_{(l)}$

If the heat capacity of the bomb calorimeter is $6.8 kJ K^{- 1}$ , the approximate enthalpy change of the reaction in $kJ {mol}^{- 1}$ is (Molar mass of glucose $= 180 g {mol}^{- 1}$ )

EASY

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

The heat of reaction for

$C_{10} H_{8} (s) + 12 O_{2} (g) ⟶ 10 {CO}_{2} (g) + 4 H_{2} O (l)$ at constant volume is $- 1228.2 kcal$ at $25^{0} C$ . The heat of reaction at constant pressure and same temperature is

HARD

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

For combustion of one mole of magnesium in an open container at

300 K

and

1

bar pressure,

Δ_{C} H^{⊖} = - 601.70 kJ {mol}^{- 1}

, the magnitude of change in internal energy for the reaction is

kJ

. (Nearest integer)
(Given :

R = 8.3 J K^{- 1} {mol}^{- 1}

)

MEDIUM

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

The internal energy change (in $J$ ) when $90 g$ of water undergoes complete evaporation at $100 ° C$ is ..............

(Given : ${ΔH}_{vap}$ for water at $373 K = 41 kJ / mol$ , $R = 8.314 {JK}^{- 1} {mol}^{- 1}$ )

MEDIUM

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

For silver,

C_{p} (J K^{- 1} m o l^{- 1}) = 23 + 0.01 T .

If the temperature

(T)

3

moles of silver is raised from

300 K t o 1000 K a t 1 a t m

pressure, the value of

Δ H

will be close to:

The heat change at constant volume for the decomposition of silver oxide is found to be 80.25 kJ . The heat change at constant pressure will be______.

Important Questions on Chemical Thermodynamics

Learn and Prepare for any exam you want !

The heat change at constant volume for the decomposition of silver oxide is found to be $80.25 kJ$ . The heat change at constant pressure will be______.