Chemistry 9th Edition

Published by Cengage Learning
ISBN 10: 1133611095
ISBN 13: 978-1-13361-109-7

Chapter 11 - Properties of Solutions - Exercises: 40

Answer

a) Enthalpy of hydration of $CaCl_2$: -2293 kJ/mol Enthalpy of hydration of $CaI_2$: -2163 kJ/mol b) $Cl^-$ is more strongly attracted to water than $I^-$.

Work Step by Step

a) The enthalpy of hydration equals the enthalpy change of solution plus the lattice energy. Using the values given, the enthalpy of hydration of $CaCl_2$ is $-46 kJ/mol + (-2247 kJ/mol) = -2293 kJ/mol$. Similarly, the enthalpy of hydration of $CaI_2$ is $-104 kJ/mol + (-2059 kJ/mol) = -2293 kJ/mol$. b) The only thing that differs between $CaCl_2$ and $CaI_2$ is the $Cl$ and $I$ atoms. Using the enthalpies of hydration calculated in part (a), it can be determined that $CaCl_2$ is more strongly attracted to water than $CaI_2$ since a lower enthalpy of hydration suggests a greater affinity for water. Because of this, it follows that $Cl^-$ must be more strongly attracted to water than $I^-$.
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