Calcium chloride is commonly used as a de-icing agent because it dissolves…
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Calcium chloride is commonly used as a de-icing agent because it dissolves exothermically in water. A chemist studies several factors that influence its dissolution.
(a) The molar enthalpy of dissolution of CaCl2 at 25 °C is –81 kJ mol−1. Predict qualitatively how the solubility of CaCl2 will change if the temperature of the water is increased from 25 °C to 60 °C. Justify your answer.
(b) Methanol has a similar dipole moment to water but a dielectric constant of only 33. When CaCl2 is added to methanol at 25 °C, far less solid dissolves than in water. Provide two reasons, at the particulate level, for this observation.
(c) An aqueous solution already contains 0.50 M NaCl. Predict whether adding NaCl will increase, decrease, or have little effect on the mass of CaCl2 that can dissolve at 25 °C. Support your prediction with an explanation that references intermolecular interactions.
(d) Identify one practical application (other than de-icing) that takes advantage of the heat released when CaCl2 dissolves, and briefly explain the chemical principle involved.