MEDIUM

Earn 100

Following data of different enthalpies are given. find the value of lattice enthalpy ( $Δ_{lattice} H^{\circ}$ ) for NaBr.

$Δ_{sub} H^{\circ}$ for sodium metal = $108.4 kJ {mol}^{- 1}$

$∆_{H_{i}}$ ( Ionisation enthalpy of sodium ) = $496 kJ {mol}^{- 1}$

$∆_{H_{eg}}$ (Electron gain enthalpy of bromine ) = $- 325 kJ {mol}^{- 1}$

Bond dissociation enthalpy of bromine = $192 kJ {mol}^{- 1}$

$Δ_{f} H^{\circ} for NaBr (s) = - 360 \cdot 1 kJ {mol}^{- 1}$

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Important Questions on Chemical Thermodynamics and Energetics

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

The enthalpy change for the conversion of

\frac{1}{2} {Cl}_{2}

(g) to

{Cl}^{-} (aq)

(-)

{kJmol}^{- 1}

(Nearest integer)
Given :

Δ_{dis} H_{{Cl}_{2 (g)}}^{0} = 240 {kJmol}^{- 1}

Δ_{eg} H_{Cl (g)}^{o} = - 350 {kJmol}^{- 1}

Δ_{hyd} H_{{Cl}_{(g)}^{-}}^{o} = - 380 {kJmol}^{- 1}

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

Given below are two statements:
Statement I : In the titration between strong acid and weak base methyl orange is suitable as an indicator.
Statement II : For titration of acetic acid with $\mathrm{NaOH}$ phenolphthalein is not a suitable indicator.
In the light of the above statements, choose the most appropriate answer from the options given below:

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

At $25 ° C$ , the enthalpy of the following processes are given:

$H_{2} (g) + O_{2} (g) \to 2 OH (g) Δ H^{o} = 78 kJ {mol}^{- 1}$

$H_{2} (g) + 1 / 2 O_{2} (g) \to H_{2} O (g) Δ H^{0} = - 242 kJ {mol}^{- 1}$

$H_{2} (g) \to 2 H (g) Δ H^{o} = 436 kJ {mol}^{- 1}$

$1 / 2 O_{2} (g) \to O (g) Δ H^{0} = 249 kJ {mol}^{- 1}$

What would be the value of X for the following reaction? (Nearest integer)

$H_{2} O (g) \to H (g) + OH (g) ∆ H^{o} = X {kJmol}^{- 1}$

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

Solid fuel used in rocket is a mixture of ${Fe}_{2} O_{3}$ and $Al$ (in ratio $1 : 2$ ). The heat evolved $(kJ)$ per gram of the mixture is _____ (Nearest integer)

Given ${ΔH}_{f}^{0} ({Al}_{2} O_{3}) = - 1700 kJ {mol}^{- 1}$

${ΔH}_{f}^{0} ({Fe}_{2} O_{3}) = - 840 kJ {mol}^{- 1}$

Molar mass of $Fe, AI$ and $O$ are $56, 27$ and $16 g {mol}^{- 1}$ respectively

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

Hess law states that,

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

Consider the following data

Heat of combustion of $H_{2} (g) = - 241.8 kJ {mol}^{- 1}$

Heat of combustion of $C (s) = - 393.5 kJ {mol}^{- 1}$

Heat of combustion of $C_{2} H_{5} OH (l)$ $= - 1234.7 kJ {mol}^{- 1}$

The heat of formation of $C_{2} H_{5} OH (l)$ is $(-)$ _____ $kJ {mol}^{- 1}$ (Nearest integer).

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

The enthalpy of combustion of propane, graphite and dihydrogen at

298 K

are:

- 2220.0 kJ {mol}^{- 1}

- 393.5 kJ {mol}^{- 1}

and

- 285.8 kJ {mol}^{- 1}

, respectively. The magnitude of enthalpy of formation of propane

(C_{3} H_{8})

is _____

{kJmol}^{- 1}

. (Nearest integer)

HARD

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

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:

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

Given

NO (g) + O_{3} (g) \to {NO}_{2} (g) + O_{2} (g) ∆ H = - 198 .9 kJ / mol

O_{3} (g) \to 3 / 2 O_{2} (g) ∆ H = - 142 .3 kJ / mol

O_{2} (g) \to 2 O (g) ∆ H = + 495 .0 kJ / mol

The enthalpy change

(∆ H)

for the following reaction is

N O (g) + O (g) \to N O_{2} (g)

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

The ionization enthalpy of

{Na}^{+}

formation from

{Na}_{(g)}

495.8 kJ {mol}^{- 1},

while the electron gain enthalpy of

Br

- 325.0 kJ {mol}^{- 1}

. Given the lattice enthalpy of

NaBr

- 728.4 kJ {mol}^{- 1}

. The energy for the formation of

NaBr

ionic solid is

(-)_____10^{- 1} kJ {mol}^{- 1}

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

Calculate the enthalpy change. For the change $8 S (g) \to S_{8} (g)$ , given that

$H_{2} S_{2} (g) \to 2 H (g) + 2 S (g), ΔH = 239 .0 k c a l m o l^{- 1}$

$H_{2} S (g) \to 2 H (g) + S (g), ΔH = 175 .0 k c a l m o l^{- 1}$

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

C (s) + O_{2} (g) \to C O_{2} (g), Δ H = - X,

C O (g) + \frac{1}{2} O_{2} (g) \to C O_{2} (g), Δ H = - Y,

Calculate

Δ_{f} H

for

C O_{(g)}

formation

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>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>Chemical Thermodynamics and Energetics>Enthalpy

Given

(A) $2 CO (g) + O_{2} (g) \to 2 {CO}_{2} (g) {ΔH}_{1}^{o} = - x kJ {mol}^{- 1}$

(B) $C (graphite) + O_{2} (g) \to {CO}_{2} (g) {ΔH}_{2}^{o} = - y kJ {mol}^{- 1}$

The $∆ H^{o}$ for the reaction $C (graphite) + \frac{1}{2} O_{2} (g) \to CO (g)$ is

HARD

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>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

)

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

One mole of ethanol is produced reacting graphite,

H_{2}

and

O_{2}

together. The standard enthalpy of formation is

- 277.7 k J m o l^{- 1} .

Calculate the standard enthalpy of the reaction when

4

moles of graphite is involved

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

Identify the INVALID equation.

HARD

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

The Born-Haber cycle for $KCl$ is evaluated with the following data:
$Δ_{f} H^{Θ} for KCl = - 436.7 {kJmol}^{- 1}; Δ_{sub} H^{Θ} for K = 89.2 {kJmol}^{- 1};$

$Δ_{ionization} H^{Θ} for K = 419.0 kJ {mol}^{- 1}; Δ_{electron gain} H^{Θ} for {Cl}_{(g)} = - 348.6 {kJmol}^{- 1}$

$Δ_{bond} H^{Θ} for {Cl}_{2} = 243.0 {kJmol}^{- 1}$
The magnitude of lattice enthalpy of $KCl$ in ${kJmol}^{- 1}$ is (Nearest integer)

EASY

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

Given that, the molar combustion enthalpy of benzene, cyclohexane and hydrogen are

x, y

and

z

, respectively, the molar enthalpy of hydrogenation of benzene to cyclohexane is

MEDIUM

Chemistry>Physical Chemistry>Chemical Thermodynamics and Energetics>Enthalpy

Given:

(i)

C (graphite) + O_{2} (g) \to {CO}_{2} (g);

{ΔrH}^{Θ} = x kJ {mol}^{- 1}

(ii)

C (graphite) + \frac{1}{2} O_{2} (g) \to CO (g);

{ΔrH}^{Θ} = y kJ {mol}^{- 1}

(iii) CO (g) + \frac{1}{2} O_{2} (g) \to {CO}_{2} (g);

{ΔrH}^{Θ} = z kJ {mol}^{- 1}

Based on the above thermochemical equations, find out which one of the following algebraic relationships is correct?

Important Questions on Chemical Thermodynamics and Energetics

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