Subjective Type

Two moles of an ideal gas are held by a piston under 10 atm pressure at 273 K. The pressure is suddenly released to 0.4 atm and the gas is allowed to expand isothermally. Calculate W, q, $$\Delta U$$ and $$\Delta H$$.

Solution

$$n= 2\ moles;\ P_i=10\ atm;\ T=273K;\ P_f=0.4atm$$

For isothermal process

$$W=-nRT (1-\dfrac{P_f}{P_i})$$

$$W=-2 \times 8.314\times273 (1-\dfrac{0.4}{10})$$

$$W=-4357.87\ J\approx -4358\ J$$

$$Q +W=\Delta U=0$$ ( In isothermal process $$\Delta E=nC\Delta T=0)$$

$$\therefore Q=-W=4358\ J$$

$$\Delta E=nC_v\Delta T=0$$ since T = constant $$\Delta=0$$

$$\Delta H=nC_p\Delta T=0$$

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