Question

The value of ΔH for cooling 2 mole of an ideal monoatomic gas from 225°C to 125°C at constant pressure will be given Cp = 5/2 R

Answer 1

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Answer to Question #67999, Physics / Molecular Physics | Thermodynamics

Question:

The value of $\Delta H$ for cooling 2 mole of an ideal monoatomic gas from $225{}^{\circ}\mathrm{C}$ to $125{}^{\circ}\mathrm{C}$ at constant pressure will be given $\mathrm{Cp} = 5/2\,\mathrm{R}$

Answer:

The enthalpy is calculated as

$$H = \vartheta C_p T$$

And so

$$\Delta H = \vartheta C_p \Delta T$$

because the pressure is constant and the gas is ideal.

$$\Delta H = \vartheta C_p \Delta T = 2 * \frac{5}{2} * 8.31 * (225 - 125) = 4155\,\mathrm{J}$$