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At $300 K$ , the standard enthalpies of formation of $C_{6} H_{5} COOH (s), {CO}_{2} (g)$ & $H_{2} O (l)$ are ; $- 408, - 393$ & $- 286 kJ {mol}^{- 1}$ respectively. Calculate the heat of combustion of benzoic acid at constant volume (in $kJ {mol}^{- 1}$ ).

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Important Questions on Thermodynamics

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Beta Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>EXERCISE-3>Q 47

The heat liberated on complete combustion of $7.8 g$ of benzene is $327 kJ$ . This heat has been measured at constant volume & at $27^{°} C$ . Calculate the heat of combustion of benzene at constant pressure (in $MJ {mol}^{- 1}$ ).

$R = 8.314 {Jmol}^{- 1} K^{- 1}$

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Beta Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>EXERCISE-3>Q 48

If the enthalpy of formation of

HCl g

and

{Cl}^{-} (aq)

are

- 92.3 kJ / mole

and

- 167.44 kJ / mol

, find the enthalpy of solution of hydrogen chloride gas in

kJ {mol}^{- 1}

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Beta Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>EXERCISE-3>Q 49

0.16 g

of methane was subjected to combustion at

27^{°} C

in a bomb calorimeter. The temperature of calorimeter system (including water) was found to rise by

0 . 5^{°} C

. Calculate the heat of combustion of methane at constant pressure (in

kJ {mol}^{- 1}

The thermal capacity of calorimeter system is $17.7 kJ K^{- 1}$ . $(R = 8.313 {mol}^{- 1} K^{- 1})$

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Beta Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>EXERCISE-3>Q 50

When

1.0 g

of fructose

C_{6} H_{12} O_{6} (s)

is burnt in oxygen in a bomb calorimeter, the temperature of the calorimeter water increases by

1 . 56^{°} C

. If the heat capacity of the calorimeter and its contents is

10.0 kJ /^{°} C

. Calculate the enthalpy of combustion of fructose at

298 K

. (in

kJ {mol}^{- 1}

)

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Beta Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>EXERCISE-3>Q 51

The enthalpy of dissociation of

{PH}_{3}

954 kJ / mol

and that of

P_{2} H_{4}

1.485 M J {mol}^{- 1}

. What is the bond enthalpy of the

P - P

bond? (in

kJ {mol}^{- 1}

)

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Beta Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>EXERCISE-3>Q 52

Using the bond enthalpy data given below, calculate the enthalpy change for the reaction, (in

kJ {mol}^{- 1}

)

$C_{2} H_{4} (g) + H_{2} (g) \to C_{2} H_{6} (g)$

Data :

Bond	$C - C$	$C = C$	$C - H$	$H - H$
Bond Enthalpy	$336.81 kJ / mol$	$606.68 kJ / mol$	$410.87 kJ / mol$	$431.79 kJ / mol$

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Beta Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>EXERCISE-3>Q 53

The enthalpy change for the following process at

25^{°} C

and under constant pressure at

1 atm

are as follows :

${CH}_{4} (g) \to C (g) + 4 H (g)$ $∆_{f} H = 396 kcal / mole$

$C_{2} H_{6} (g) \to 2 C (g) + 6 H (g)$

$∆_{f} H = 676 kcal / mole$

Calculate $C - C$ bond energy in $C_{2} H_{6}$ (in $kcal {mol}^{- 1}$ )

Given : $∆_{sub} C (s) = 171.8 kcal / mole$

$B . E . (H - H) = 104.1 kcal / mole$

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Beta Question Bank for Engineering: Chemistry>Chapter 4 - Thermodynamics>EXERCISE-3>Q 54

Find the enthalpy of

S - S

bond (in

kJ {mol}^{- 1}

) from the following data.

(i) $C_{2} H_{5} - S - C_{2} H_{5} (g) ∆ H_{f}^{°} = + 147.2 kJ / mol$

(ii) $C_{2} H_{5} - S - S - C_{2} H_{2} (g) ∆ H_{f}^{°} = + 201.9 kJ / mol$

(iii) $S (g) ∆ H_{f}^{°} = + 222.8 kJ / mol$

At 300K, the standard enthalpies of formation of C6H5COOHs, CO2g & H2Ol are ; -408,-393 & -286 kJ mol-1 respectively. Calculate the heat of combustion of benzoic acid at constant volume (in kJ mol-1).

Important Questions on Thermodynamics

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At $300 K$ , the standard enthalpies of formation of $C_{6} H_{5} COOH (s), {CO}_{2} (g)$ & $H_{2} O (l)$ are ; $- 408, - 393$ & $- 286 kJ {mol}^{- 1}$ respectively. Calculate the heat of combustion of benzoic acid at constant volume (in $kJ {mol}^{- 1}$ ).