(C) The molar mass of $n$-octane $(C_8H_{18})$ is $114 \ g \ mol^{-1}$.Number of moles of octane $= \frac{1.14 \ g}{114 \ g \ mol^{-1}} = 0.01 \ mol$.

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(C) The molar mass of $n$-octane $(C_8H_{18})$ is $114 \ g \ mol^{-1}$.Number of moles of octane $= \frac{1.14 \ g}{114 \ g \ mol^{-1}} = 0.01 \ mol$.Heat evolved $(q) = C \times \Delta T$,where $C = 5 \ kJ \ K^{-1}$ and $\Delta T = 5 \ K$.$q = 5 \times 5 = 25 \ kJ$.The heat of combustion at constant volume $(\Delta U)$ is the heat evolved per mole.$\Delta U = \frac{25 \ kJ}{0.01 \ mol} = 2500 \ kJ \ mol^{-1}$.

Class 11 Chemistry Thermodynamics Mix Examples-Thermodynamics and Thermochemistry

Medium

$A$ sample of $n$-octane $(1.14 \ g)$ was completely burnt in excess of oxygen in a bomb calorimeter,whose heat capacity is $5 \ kJ \ K^{-1}$. As a result of the combustion reaction,the temperature of the calorimeter increased by $5 \ K$. The magnitude of the heat of combustion of octane at constant volume is $.......... \ kJ \ mol^{-1}$ (nearest integer).

JEE MAIN 2025 All JEE MAIN

A
$2100$
B
$2200$
C
$2500$
D
$2600$

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Mix Examples-Thermodynamics and Thermochemistry

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The heat of vaporisation and heat of fusion of $H_2O$ are $540 \, cal/g$ and $80 \, cal/g$. The ratio of $\frac{\Delta S_{vap}}{\Delta S_{fusion}}$ for water is :-

Medium

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Calculate the standard internal energy change for $OF_{2(g)} + H_2O_{(g)} \longrightarrow 2 HF_{(g)} + O_{2(g)}$ at $300 \ K$,if $\Delta_{f} H^{\circ}$ of $OF_{2(g)}$,$H_2O_{(g)}$,and $HF_{(g)}$ are $20$,$-250$,and $-270 \ kJ \ mol^{-1}$ respectively. $[R = 8.314 \ J \ K^{-1} \ mol^{-1}]$ (in $kJ$)

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For the reaction $2A_{(g)} + B_{(g)} \to 2D_{(g)}$,given $\Delta U^{\theta} = -10.5 \ kJ$ and $\Delta S^{\theta} = -44.1 \ J \ K^{-1}$. Calculate $\Delta G^{\theta}$ for the reaction at $298 \ K$ and predict whether the reaction may occur spontaneously.

Medium

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At $1 \ atm$ pressure,$\Delta S = 75 \ J/K \cdot mol$ and $\Delta H = 30 \ kJ/mol$. The temperature of the reaction at equilibrium is $....... \ K$.

Easy

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Which of the following is/are true about the reversible isothermal expansion of an ideal gas?
$(a) \ \Delta U = 0$
$(b) \ q = 0$
$(c) \ \Delta T = 0$
$(d) \ q = 2.303 \ nRT \ \log_{10} \left( \frac{V_2}{V_1} \right)$

Medium

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The heat of vaporisation and heat of fusion of $H_2O$ are $540 \, cal/g$ and $80 \, cal/g$. The ratio of $\frac{\Delta S_{vap}}{\Delta S_{fusion}}$ for water is :-

Calculate the standard internal energy change for $OF_{2(g)} + H_2O_{(g)} \longrightarrow 2 HF_{(g)} + O_{2(g)}$ at $300 \ K$,if $\Delta_{f} H^{\circ}$ of $OF_{2(g)}$,$H_2O_{(g)}$,and $HF_{(g)}$ are $20$,$-250$,and $-270 \ kJ \ mol^{-1}$ respectively. $[R = 8.314 \ J \ K^{-1} \ mol^{-1}]$ (in $kJ$)

For the reaction $2A_{(g)} + B_{(g)} \to 2D_{(g)}$,given $\Delta U^{\theta} = -10.5 \ kJ$ and $\Delta S^{\theta} = -44.1 \ J \ K^{-1}$. Calculate $\Delta G^{\theta}$ for the reaction at $298 \ K$ and predict whether the reaction may occur spontaneously.

At $1 \ atm$ pressure,$\Delta S = 75 \ J/K \cdot mol$ and $\Delta H = 30 \ kJ/mol$. The temperature of the reaction at equilibrium is $....... \ K$.

Which of the following is/are true about the reversible isothermal expansion of an ideal gas?$(a) \ \Delta U = 0$$(b) \ q = 0$$(c) \ \Delta T = 0$$(d) \ q = 2.303 \ nRT \ \log_{10} \left( \frac{V_2}{V_1} \right)$

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Which of the following is/are true about the reversible isothermal expansion of an ideal gas?
$(a) \ \Delta U = 0$
$(b) \ q = 0$
$(c) \ \Delta T = 0$
$(d) \ q = 2.303 \ nRT \ \log_{10} \left( \frac{V_2}{V_1} \right)$