Describe the enthalpy changes during the dissolving of NaCl into CH4: A. The ent

Question

Describe the enthalpy changes during the dissolving of NaCl into CH4:

A. The enthalpy of separating the solute is highly endothermic; the enthalpy of separating the solvent is slightly endothermic; the enthalpy of mixing is slightly exothermic; the enthalpy of solution is highly endothermic.

B. The enthalpy of separating the solute is slightly endothermic; the enthalpy of separating the solvent is highly endothermic; the enthalpy of mixing is slightly exothermic; the enthalpy of solution is highly endothermic.

C. The enthalpy of separating the solute is highly endothermic; the enthalpy of separating the solvent is slightly endothermic; the enthalpy of mixing is highly exothermic; the enthalpy of solution is slightly endothermic.

D. The enthalpy of separating the solute is slightly endothermic; the enthalpy of separating the solvent is slightly endothermic; the enthalpy of mixing is highly exothermic; the enthalpy of solution is highly exothermic.

Explanation / Answer

The answer is:

A. The enthalpy of separating the solute is highly endothermic; the enthalpy of separating the solvent is slightly endothermic; the enthalpy of mixing is slightly exothermic; the enthalpy of solution is highly endothermic.

Separating ionic NaCl solute => high energy needed => highly endothermic

Separating molecular CH4 solvent (dispersion forces) => low energy needed => slightly endothermic

Mixing incompatible bond types (ionic and dispersion forces) => low energy released => slightly exothermic

Enthalpy of solution = sum of energies above = highly endothermic

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