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Water is added to a flask containing solid NH4CI. As the
Chapter 14, Problem 16P(choose chapter or problem)
Problem 16P
Water is added to a flask containing solid NH4CI. As the salt dissolves, the solution becomes colder.
(a) Is the dissolving of NH4Cl exothermic or endothermic?
(b) Is the magnitude of ΔHlattice of NH4Cl larger or smaller than the combined ΔHhydr of the ions? Explain.
(c) Given the answer to (a), why does NH4Cl dissolve in water?
Questions & Answers
QUESTION:
Problem 16P
Water is added to a flask containing solid NH4CI. As the salt dissolves, the solution becomes colder.
(a) Is the dissolving of NH4Cl exothermic or endothermic?
(b) Is the magnitude of ΔHlattice of NH4Cl larger or smaller than the combined ΔHhydr of the ions? Explain.
(c) Given the answer to (a), why does NH4Cl dissolve in water?
ANSWER:
Solution 16P:
Step 1: Hydration is a process where the solute molecule is surrounded by the water molecules.
Thus, the enthalpy changes for the solution () is equal to the sum of the heat of hydration (
) and heat of solute (
).