Some properties of potassium metal are summarized in the...

Some properties of potassium metal are summarized in the following table: $$\begin{array}{lr}{\text { Normal melting point }} & {63.5^{\circ} \mathrm{C}} \\ {\text { Normal boiling point }} & {765.7^{\circ} \mathrm{C}}\end{array}$$ $$\begin{array}{ll}{\text { Molar heat of fusion }} & {2.334 \mathrm{kJ} / \mathrm{mol}} \\ {\text { Molar heat of vaporization }} & {79.87 \mathrm{kJ} / \mathrm{mol}} \\ {\text { Specific heat of the solid }} & {0.75 \mathrm{J} / \mathrm{g}^{\circ} \mathrm{C}}\end{array}$$ a. Calculate the quantity of heat required to heat 5.00 g of potassium from $25.3^{\circ}$ " to $45.2^{\circ} \mathrm{C}$ . b. Calculate the quantity of heat required to melt 1.35 moles of potassium at its normal melting point. c. Calculate the quantity of heat required to vaporize 2.25 g of potassium at its normal boiling point.

Some properties of potassium metal are summarized in the following table:
$$\begin{array}{lr}{\text { Normal melting point }} & {63.5^{\circ} \mathrm{C}} \\ {\text { Normal boiling point }} & {765.7^{\circ} \mathrm{C}}\end{array}$$
$$\begin{array}{ll}{\text { Molar heat of fusion }} & {2.334 \mathrm{kJ} / \mathrm{mol}} \\ {\text { Molar heat of vaporization }} & {79.87 \mathrm{kJ} / \mathrm{mol}} \\ {\text { Specific heat of the solid }} & {0.75 \mathrm{J} / \mathrm{g}^{\circ} \mathrm{C}}\end{array}$$
a. Calculate the quantity of heat required to heat 5.00 g of potassium from $25.3^{\circ}$ " to $45.2^{\circ} \mathrm{C}$ .
b. Calculate the quantity of heat required to melt 1.35 moles of potassium at its normal melting point.
c. Calculate the quantity of heat required to vaporize 2.25 g of potassium at its normal boiling point.

Key Concepts

Specific Heat Capacity

Specific heat capacity is the amount of heat required to raise the temperature of one gram (or one mole, depending on units) of a substance by one degree Celsius (or one Kelvin). This concept is essential for calculating the heat needed to change a substance's temperature without altering its phase, based on the mass of the substance and the temperature change involved.

Heat of Fusion

The heat of fusion is the amount of energy required to change a substance from a solid state to a liquid state at its melting point without changing its temperature. This concept is critical for calculations involving phase transitions where the substance is melted, and it helps in quantifying the energy involved in overcoming the forces that keep the substance in its solid form.

Heat of Vaporization

The heat of vaporization is defined as the amount of energy needed to transform a substance from the liquid phase to the gas phase at its boiling point without a change in temperature. This concept is used to determine how much energy is absorbed during the phase change from liquid to vapor, which is crucial for understanding and calculating processes that involve boiling or evaporation.

Calorimetry

Calorimetry is the experimental technique used to measure the quantity of heat exchanged in chemical reactions or physical changes, such as temperature variations and phase transitions. It provides a framework for applying the principles of specific heat, heat of fusion, and heat of vaporization to determine the energy changes in a system, making it indispensable in studies of thermodynamics and heat transfer.

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