Chapter 6

(a) Near room temperature the specific heat capacity of ethanol is \(2.42 \mathrm{~J} \cdot\left({ }^{\circ} \mathrm{C}\right)^{-1} \cdot \mathrm{g}^{-1}\). Calculate the heat that must be removed to reduce the temperature of \(150.0 \mathrm{~g}\) of \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{OH}\) from \(50.0^{\circ} \mathrm{C}\) to \(16.6^{\circ} \mathrm{C}\). (b) What mass of copper can be heated from \(15^{\circ} \mathrm{C}\) to \(205^{\circ} \mathrm{C}\) when \(425 \mathrm{~kJ}\) of energy is available?

Near room temperature, the specific heat capacity of benzene is \(1.05 \mathrm{~J} \cdot\left({ }^{\circ} \mathrm{C}\right)^{-1} \mathrm{~g}^{-1}\). Calculate the heat nceded to raise the temperature of \(50.0 \mathrm{~g}\) of benzene from \(25.3^{\circ} \mathrm{C}\) to \(37.2^{\circ} \mathrm{C}\). (b) A \(1.0-\mathrm{kg}\) block of aluminum is supplied with \(490 \mathrm{~kJ}\) of heat. What is the temperature change of the aluminum? The specific heat capacity of aluminum is \(0.90 \mathrm{~J} \cdot\left({ }^{\circ} \mathrm{C}\right)^{-1} \cdot \mathrm{g}^{-1}\).

A piece of metal of mass \(20.0 \mathrm{~g}\) at \(100.0^{\circ} \mathrm{C}\) is placed in a calorimeter containing \(50.7 \mathrm{~g}\) of watcr at \(22.0^{\circ} \mathrm{C}\). The final temperature of the mixture is \(25.7^{\circ} \mathrm{C}\) What is the specific heat capacity of the mctal? Assume that all the energy lost by the metal is gained by the water.

A calorimeter was calibrated with an electric heater, which was used to supply \(22.5 \mathrm{~kJ}\) of energy to the calorimeter; the heat increased the temperature of the calorimeter and its water bath from \(22.45^{\circ} \mathrm{C}\) to \(23.97^{\circ} \mathrm{C}\). What is the heat capacity of the calorimeter?

Calculate the amount of heat needed to raise the temperature of \(0.325 \mathrm{~mol}\) of a monatomic idcal gas from a temperature of \(-25^{\circ} \mathrm{C}\) to \(+50^{\circ} \mathrm{C}\) at (a) constant volume and (b) constant pressure. (c) Why is more heat needed to raise the temperature at constant pressure than at constant volume?

A calorimeter has a measured heat capacity of \(6.27 \mathrm{~kJ} \cdot\left({ }^{\circ} \mathrm{C}\right)^{-1}\). The combustion of \(1.84 \mathrm{~g}\) of magnesium led to a temperature change from \(21.30^{\circ} \mathrm{C}\) to \(28.56^{\circ} \mathrm{C}\). Calculare the enthalpy change of the reaction \(2 \mathrm{Mg}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{MgO}(\mathrm{s})\).

Which gas do you expect to have the higher molar heat capacity, \(\mathrm{NO}\) or \(\mathrm{NO}_{2}\) ? Why?

(a) At its boiling point, the vaporization of \(0.235 \mathrm{~mol} \mathrm{CH}_{4}(1)\) requires \(1.93 \mathrm{~kJ}\) of heat. What is the enthalpy of vaporization of methane? (b) An electric heater was immersed in a flask of boiling crhanol, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\), and \(22.45 \mathrm{~g}\) of ethanol was vaporized when \(21.2 \mathrm{~kJ}\) of energy was supplied. What is the enthalpy of vaporization of ethanol?

(a) At its boiling point, the vaporization of \(0.235 \mathrm{~mol} \mathrm{CH}_{4}(1)\) requires \(1.93 \mathrm{~kJ}\) of heat. What is the enthalpy of vaporization of methane? (b) An electric heater was immersed in a flask of boiling crhanol, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\), and \(22.45 \mathrm{~g}\) of ethanol was vaporized when \(21.2 \mathrm{~kJ}\) of energy was supplied. What is the enthalpy of vaporization of ethanol?

The standard enthalpies of combustion of graphite and diamond are \(-393.51\) and \(-395.41 \mathrm{~kJ} \cdot \mathrm{mol}^{-1}\), respectively. Calculate the change in molar enthalpy for the graphite \(\rightarrow\) diamond transition.