(B) The entropy change for a phase transition is given by $\Delta S = \frac{\Delta H}{T}$.For fusion: $x = \frac{\Delta H_{\text{fus}}}{T_{\text{m.p}}

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(B) The entropy change for a phase transition is given by $\Delta S = \frac{\Delta H}{T}$.For fusion: $x = \frac{\Delta H_{\text{fus}}}{T_{\text{m.p}}} = \frac{10.9 \times 1000 \ J \ mol^{-1}}{278.65 \ K} \approx 39.12 \ JK^{-1} \ mol^{-1}$.For vaporisation: $y = \frac{\Delta H_{\text{vap}}}{T_{\text{b.p}}} = \frac{31.0 \times 1000 \ J \ mol^{-1}}{353.15 \ K} \approx 87.78 \ JK^{-1} \ mol^{-1}$.The value of $(y-x) = 87.78 - 39.12 = 48.66 \ JK^{-1} \ mol^{-1}$.

Class 11 Chemistry Thermodynamics Mix Examples-Thermodynamics and Thermochemistry

Medium

The molar heats of fusion and vaporisation of benzene are $10.9$ and $31.0 \ kJ \ mol^{-1}$ respectively. The changes in entropy for the solid $\rightarrow$ liquid and liquid $\rightarrow$ vapour transitions for benzene are $x$ and $y \ JK^{-1} \ mol^{-1}$,respectively. The value of $(y-x)$ (in $JK^{-1} \ mol^{-1}$) is (At $1 \ atm$,benzene melts at $5.5^{\circ} C$ and boils at $80^{\circ} C$).

AP EAMCET 2024 All AP EAMCET

A
$87.8$
B
$48.7$
C
$39.1$
D
$28.7$

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Mix Examples-Thermodynamics and Thermochemistry

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The molar heat of neutralization of $NaOH$ with $HCl$ in comparison to that of $KOH$ with $HNO_3$ is:

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One mole of an ideal gas is allowed to expand reversibly and adiabatically from a temperature of $27\,^oC$. If the work done during the process is $3\,kJ$,the final temperature will be equal to $(C_v = 20\,J\,K^{-1} \, mol^{-1})$

MediumAIIMS 2001

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For the reaction,$2 CO + O_2 \longrightarrow 2 CO_2$; $\Delta H = -560 \ kJ$. Two moles of $CO$ and one mole of $O_2$ are taken in a container of volume $1 \ L$. They completely form two moles of $CO_2$. The gases deviate appreciably from ideal behavior. If the pressure in the vessel changes from $70 \ atm$ to $40 \ atm$,find the magnitude (absolute value) of $\Delta U$ at $500 \ K$. $(1 \ L \ atm = 0.1 \ kJ)$

IIT 2006

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$A$ gas present in a cylinder expands against a constant pressure of $1 \, atm$ from a volume of $2 \, L$ to a volume of $6 \, L$. In doing so,it absorbs $800 \, J$ of heat from the surroundings. The change in internal energy of the process is ....... $J$.

Medium

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$X \, g$ of ice at $0^{\circ} C$ is added to $340 \, g$ of water at $20^{\circ} C$. The final temperature of the resultant mixture is $5^{\circ} C$. The value of $X$ (in $g$) is closest to:
[Heat of fusion of ice $= 333 \, J / g$; specific heat of water $= 4.184 \, J / g \cdot K$]

MediumKVPY 2017

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The molar heat of neutralization of $NaOH$ with $HCl$ in comparison to that of $KOH$ with $HNO_3$ is:

One mole of an ideal gas is allowed to expand reversibly and adiabatically from a temperature of $27\,^oC$. If the work done during the process is $3\,kJ$,the final temperature will be equal to $(C_v = 20\,J\,K^{-1} \, mol^{-1})$

$A$ gas present in a cylinder expands against a constant pressure of $1 \, atm$ from a volume of $2 \, L$ to a volume of $6 \, L$. In doing so,it absorbs $800 \, J$ of heat from the surroundings. The change in internal energy of the process is ....... $J$.

$X \, g$ of ice at $0^{\circ} C$ is added to $340 \, g$ of water at $20^{\circ} C$. The final temperature of the resultant mixture is $5^{\circ} C$. The value of $X$ (in $g$) is closest to:[Heat of fusion of ice $= 333 \, J / g$; specific heat of water $= 4.184 \, J / g \cdot K$]

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$X \, g$ of ice at $0^{\circ} C$ is added to $340 \, g$ of water at $20^{\circ} C$. The final temperature of the resultant mixture is $5^{\circ} C$. The value of $X$ (in $g$) is closest to:
[Heat of fusion of ice $= 333 \, J / g$; specific heat of water $= 4.184 \, J / g \cdot K$]