You are planning a lecture demonstration to illustrate an...

You are planning a lecture demonstration to illustrate an endothermic process. You want to lower the temperature of $1400 \mathrm{mL}$ water in an insulated container from 25 to $10^{\circ} \mathrm{C} .$ Approximately what mass of $\mathrm{NH}_{4} \mathrm{Cl}(\mathrm{s})$ should you dissolve in the water to achieve this result? The heat of solution of $\mathrm{NH}_{4} \mathrm{Cl}$ is $+14.7 \mathrm{kJ} / \mathrm{mol} \mathrm{NH}_{4} \mathrm{Cl}$

You are planning a lecture demonstration to illustrate an endothermic process. You want to lower the temperature of $1400 \mathrm{mL}$ water in an insulated container from 25 to
$10^{\circ} \mathrm{C} .$ Approximately what mass of $\mathrm{NH}_{4} \mathrm{Cl}(\mathrm{s})$ should you dissolve in the water to achieve this result? The heat of solution of $\mathrm{NH}_{4} \mathrm{Cl}$ is $+14.7 \mathrm{kJ} / \mathrm{mol} \mathrm{NH}_{4} \mathrm{Cl}$

Key Concepts

Heat of Solution

The heat of solution is defined as the enthalpy change associated with dissolving a substance in a solvent to form a solution. When a substance dissolves endothermically, it absorbs a specific amount of heat per mole from its surroundings. This concept is crucial in applications where a salt or solute is used to induce a temperature change by absorbing heat energy upon dissolution.

Specific Heat Capacity

Specific heat capacity is a property that indicates the amount of heat required to change the temperature of a unit mass of a substance by one degree Celsius (or Kelvin). It is a key parameter in calorimetric calculations, as it allows the conversion of temperature changes into the quantity of energy involved in heating or cooling processes.

Stoichiometric Calculations

Stoichiometric calculations involve converting between the amounts of reactants and products in a chemical process using mole-to-mass conversion. In the context of heat changes, these calculations allow one to determine the necessary mass of a substance (based on its molar heat of solution and molar mass) needed to achieve a desired amount of energy change or temperature shift in the system.

Endothermic Process

An endothermic process is one in which a chemical or physical change absorbs heat energy from its surroundings. This absorption of energy typically results in a decrease in the temperature of the surroundings, making it a useful concept for demonstrations and practical applications such as refrigeration or cooling effects in chemical solutions.

Calorimetry

Calorimetry is the measurement of the amount of heat exchanged in chemical and physical processes. It involves calculations using the specific heat capacity of substances and is foundational for determining energy changes during a reaction. In a calorimeter, heat exchange is carefully monitored, which allows us to relate temperature changes to the energy absorbed or released.

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