Thermodynamics Questions | JEE Main Chemistry Chapter Wise Question Papers

Q 1 :
Choose the correct option for free expansion of an ideal gas under adiabatic condition from the following: [2024]

$q = 0, Δ T \neq 0, w = 0$
$q = 0, Δ T < 0, w \neq 0$
$q \neq 0, Δ T = 0, w = 0$
$q = 0, Δ T = 0, w = 0$

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(D) For adiabatic process $q = 0$ .

$W = - P_{ext} Δ V, for free expansion, P_{ext} = 0, so w = 0$

By first law of thermodynamics:

$Δ U = W + q$

$Δ U = 0 + 0 = 0$

For an ideal gas internal energy is function of temperature, so if $Δ U = 0, Δ T$ is also 0.

Q 2 :
If 5 moles of an ideal gas expands from 10 L to a volume of 100 L at 300 K under isothermal and reversible condition then work, w, is $- x$ J. The value of $x$ is _________ .

(Given R = 8.314 J $K^{- 1}$ $m o l^{- 1}$ ) [2024]

0%

(28721)

For isothermal reversible process, work W is given by:

$W = - 2.303$ $n R T$ $\log$ $\frac{V_{2}}{V_{1}}$

$= - 2.303 \times 5$ $mol \times 8.314 \frac{J}{mol K} \times 300$ $K$ $l o g$ $\frac{100}{10}$

$= - 28720.713$ $J \approx - 28721 J$

Q 3 :
The heat of combustion of solid benzoic acid at constant volume is –321.30 kJ at 27°C. The heat of combustion at constant pressure is (–321.30 – $x$ R) kJ, the value of $x$ is _________ . [2024]

0%

(150)

$C_{6} H_{5} COOH (s) + \frac{15}{2} O_{2} (g) \to 7 {CO}_{2} (g) + 3 H_{2} O (l)$

$Δ n_{g} = Gaseous moles of products - Gaseous moles of reactants$

$= 7 - 7.5 = - 0.5$

$Heat of combustion at constant pressure (Δ H) is related to heat of combustion at constant volume (Δ U) by :$

$Δ H = Δ U + Δ n_{g} R T$

$Δ H = - 321.3 - 0.5 R \times 300$

$Δ H = - 321.3 - 150 R$

Q 4 :
$Δ_{vap} H^{Θ}$ for water is + 40.79 kJ $m o l^{- 1}$ at 1 bar and 100°C. Change in internal energy for this vapourisation under same condition is ________ kJ $m o l^{- 1}$ . (Integer answer)

(Given R = 8.3 $J K^{- 1}$ $m o l^{- 1}$ ) [2024]

0%

(38)

$H_{2} O (l) ⇌ H_{2} O (g)$

$Δ n_{g} = Gaseous moles of products - Gaseous moles of reactants$

$= 1 - 0 = 1$

$Δ H = Δ U + Δ n_{g} R T$

$40.79 {kJmol}^{- 1} = Δ U + 1 \times 8.3 \frac{J}{molK} \times 373 K$

$40.79 {kJmol}^{- 1} = Δ U + 1 \times \frac{8.3}{1000} \frac{kJ}{molK} \times 373 K$

$Δ U = 37.69 {kJmol}^{- 1} \approx 38 {kJmol}^{- 1}$

Topic Question Set

Q 1 :
Choose the correct option for free expansion of an ideal gas under adiabatic condition from the following: [2024]

Q 2 :
If 5 moles of an ideal gas expands from 10 L to a volume of 100 L at 300 K under isothermal and reversible condition then work, w, is $- x$ J. The value of $x$ is _________ .

(Given R = 8.314 J $K^{- 1}$ $m o l^{- 1}$ ) [2024]

0%

Q 3 :
The heat of combustion of solid benzoic acid at constant volume is –321.30 kJ at 27°C. The heat of combustion at constant pressure is (–321.30 – $x$ R) kJ, the value of $x$ is _________ . [2024]

0%

Q 4 :
$Δ_{vap} H^{Θ}$ for water is + 40.79 kJ $m o l^{- 1}$ at 1 bar and 100°C. Change in internal energy for this vapourisation under same condition is ________ kJ $m o l^{- 1}$ . (Integer answer)

(Given R = 8.3 $J K^{- 1}$ $m o l^{- 1}$ ) [2024]

0%

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Topic Question Set

Q 1 : Choose the correct option for free expansion of an ideal gas under adiabatic condition from the following: [2024]

Q 2 : If 5 moles of an ideal gas expands from 10 L to a volume of 100 L at 300 K under isothermal and reversible condition then work, w, is -x J. The value of x is _________ . (Given R = 8.314 J K-1 mol-1) [2024]

0%

Q 3 : The heat of combustion of solid benzoic acid at constant volume is –321.30 kJ at 27°C. The heat of combustion at constant pressure is (–321.30 – xR) kJ, the value of x is _________ . [2024]

0%

Q 4 : ΔvapHΘ for water is + 40.79 kJ mol-1 at 1 bar and 100°C. Change in internal energy for this vapourisation under same condition is ________ kJ mol-1. (Integer answer) (Given R = 8.3 JK-1 mol-1) [2024]

0%

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Q 1 :
Choose the correct option for free expansion of an ideal gas under adiabatic condition from the following: [2024]

Q 2 :
If 5 moles of an ideal gas expands from 10 L to a volume of 100 L at 300 K under isothermal and reversible condition then work, w, is $- x$ J. The value of $x$ is _________ .

(Given R = 8.314 J $K^{- 1}$ $m o l^{- 1}$ ) [2024]

Q 3 :
The heat of combustion of solid benzoic acid at constant volume is –321.30 kJ at 27°C. The heat of combustion at constant pressure is (–321.30 – $x$ R) kJ, the value of $x$ is _________ . [2024]

Q 4 :
$Δ_{vap} H^{Θ}$ for water is + 40.79 kJ $m o l^{- 1}$ at 1 bar and 100°C. Change in internal energy for this vapourisation under same condition is ________ kJ $m o l^{- 1}$ . (Integer answer)

(Given R = 8.3 $J K^{- 1}$ $m o l^{- 1}$ ) [2024]