(A) According to the first law of thermodynamics,the change in internal energy $\Delta U$ is given by $\Delta U = q + w$. For a cyclic process,$\Delta

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The first law of thermodynamics is not violated.

(A) According to the first law of thermodynamics,the change in internal energy $\Delta U$ is given by $\Delta U = q + w$. For a cyclic process,$\Delta U = 0$,which implies $q = -w$ or $w = -q$. Here,the total heat absorbed is $q_{total} = Q_1 + Q_2$. Therefore,the work done by the engine should be $W = -(Q_1 + Q_2)$. The given expression $W = Q_1 + Q_2$ implies $W = -q_{total}$,which is consistent with the first law of thermodynamics for a cyclic process where the system returns to its initial state. Thus,the first law is not violated.

Class 11 Chemistry Thermodynamics First law of thermodynamics

Easy

An engine absorbs heat $Q_1$ at temperature $T_1$ and heat $Q_2$ at temperature $T_2$. The work done by the engine is given as $W = Q_1 + Q_2$. Which of the following statements is correct?

A
The first law of thermodynamics is not violated.
B
If $Q_1$ is negative,the first law of thermodynamics is violated.
C
If $Q_2$ is negative,the first law of thermodynamics is violated.
D
The first law of thermodynamics is violated.

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Thermodynamics

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First law of thermodynamics

The heat change for the following reaction at $298 \ K$ and at constant pressure is $+7.3 \ kcal$: $A_2B_{(s)} \to 2A_{(s)} + 1/2B_{2(g)}$,$\Delta H = +7.3 \ kcal$. The heat change at constant volume would be:

Medium

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For water $\Delta_{vap} H = 41 \ kJ \ mol^{-1}$ at $373 \ K$ and $1 \ bar$ pressure. Assuming that water vapour is an ideal gas that occupies a much larger volume than liquid water,the internal energy change during evaporation of water is $...... \ kJ \ mol^{-1}$.
[Use: $R = 8.3 \ J \ mol^{-1} \ K^{-1}$]

MediumJEE MAIN 2021

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For the reaction $CO_{(g)} + \frac{1}{2} O_{2(g)} \rightarrow CO_{2(g)}$ at constant temperature and pressure,which of the following statements is correct?

Easy

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$A$ gas undergoes a change from state $A$ to state $B$. In this process,the heat absorbed and work done by the gas are $5\, J$ and $8\, J$,respectively. Now,the gas is brought back to $A$ by another process during which $3\, J$ of heat is evolved. In this reverse process of $B$ to $A$:

DifficultJEE MAIN 2017

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When $1 \ mol$ of ice melts at $0 \ ^oC$ and a constant pressure of $1 \ atm$,the system absorbs $1440 \ cal$ of heat. If the molar volumes of ice and water are $0.0196 \ L$ and $0.0180 \ L$ respectively,calculate the change in internal energy $(\Delta U)$ of the system in $cal$.

Medium

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An engine absorbs heat $Q_1$ at temperature $T_1$ and heat $Q_2$ at temperature $T_2$. The work done by the engine is given as $W = Q_1 + Q_2$. Which of the following statements is correct?

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The heat change for the following reaction at $298 \ K$ and at constant pressure is $+7.3 \ kcal$: $A_2B_{(s)} \to 2A_{(s)} + 1/2B_{2(g)}$,$\Delta H = +7.3 \ kcal$. The heat change at constant volume would be:

For the reaction $CO_{(g)} + \frac{1}{2} O_{2(g)} \rightarrow CO_{2(g)}$ at constant temperature and pressure,which of the following statements is correct?

$A$ gas undergoes a change from state $A$ to state $B$. In this process,the heat absorbed and work done by the gas are $5\, J$ and $8\, J$,respectively. Now,the gas is brought back to $A$ by another process during which $3\, J$ of heat is evolved. In this reverse process of $B$ to $A$:

When $1 \ mol$ of ice melts at $0 \ ^oC$ and a constant pressure of $1 \ atm$,the system absorbs $1440 \ cal$ of heat. If the molar volumes of ice and water are $0.0196 \ L$ and $0.0180 \ L$ respectively,calculate the change in internal energy $(\Delta U)$ of the system in $cal$.

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