Question 10 • 26-27 - C - RUSD Chemistry in the Earth System
The triangle cap h sub sol for NaF is 82 kJ/mol , and the lattice energy is negative 923 kJ/mol If the hydration enthalpy of sodium is 21 kJ/mol more than the hydration enthalpy of fluoride, what are the hydration enthalpies for the sodium and fluoride ions? Use triangle cap h sub sol is equal to negative triangle cap h sub lat plus triangle cap h sub hydr
Using ΔHsol = −ΔHlat + ΔHhydr, the total hydration enthalpy is 82 − 923 = −841 kJ/mol. Let the fluoride hydration enthalpy be x; sodium’s is x + 21. Then 2x + 21 = −841, so fluoride is −431 kJ/mol and sodium is −410 kJ/mol. Choice C gives these values.
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