MediumChemistryHigh School (11–12)Chemical Thermodynamics › Enthalpy and Hess's LawNumerical

Argon is close to an ideal gas, with Cv = 12.47 J K⁻¹mol⁻¹.

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

Argon is close to an ideal gas, with $C_v = 12.47\ \text{J K}^{-1}\text{mol}^{-1}$ . Find $C_p$ . How much heat warms $2.00\ \text{mol}$ of argon by $15\ \text{K}$ at constant volume, and how much at constant pressure? Where does the extra heat go?

Need a reminder? The key ideaShow

At constant pressure the heat taken in is $\Delta H$ , and at constant volume it is $\Delta U$ . For gases, $\Delta H = \Delta U + \Delta n_g R T$ , where $\Delta n_g$ counts moles of gas only and $R = 8.314\ \text{J K}^{-1}\text{mol}^{-1}$ . Heat and temperature are linked by $q = C\Delta T = m c \Delta T$ . A calorimeter takes up the heat the reaction gives out, so $\Delta H = -q$ per mole. For an ideal gas, $C_p - C_v = R$ .

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

← All Problems

← 0.600 g of graphite burns completely in a bomb calorimeter whose heat capacity is 12.5 kJ K⁻¹.Ethanol burns as C₂H₅OH(l) + 3O₂(g) → 2CO₂(g) + 3H₂O(l). →

More onChemical Thermodynamics › Enthalpy and Hess's Law

Discussion (0)

Loading…

Argon is close to an ideal gas, with Cv = 12.47 J K⁻¹mol⁻¹.

The worked solution

Discussion (0)

Want to go further in Chemical Thermodynamics › Enthalpy and Hess's Law?