One type of chemical heat pack is made by sealing water (H2O) and calcium chloride (CaCl2) in...


One type of chemical heat pack is made by sealing water {eq}(H_2O) {/eq} and calcium chloride {eq}(CaCl_2) {/eq} in separate compartments. When the membrane between the components is broken and the substances are allowed to mix, there is a large amount of heat produced. Is this a chemical or physical change? Explain.

Enthalpy of Solution:

The enthalpy of solution is the heat change that occurs when a certain substance is dissolved as a solute in another substance acting as the solvent, with the dissolution process at constant pressure. This heat change occurs due to the breaking of solute-solute and solvent-solvent interactions, followed by the formation of solute-solvent interactions during solvation. In most cases the solvent is liquid water and the value is quoted per mole of the solute. If this net heat change is positive/negative, then the dissolution process is endothermic/exothermic and the solution temperature will be lower/higher than the initial solvent alone.

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The key to answering this question lies in the composition of calcium chloride. It is an ionic (salt) compound, which in the solid form has a...

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Enthalpy: Energy Transfer in Physical and Chemical Processes


Chapter 13 / Lesson 2

When energy is transferred during a chemical reaction, it is called enthalpy. Examine the changes that happen, the relationship to energy, heat, and temperature, exothermic and endothermic processes, and physical and chemical changes during enthalpy.

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