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M5 Lattice Enthalpy Q&A

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Total cards: 6•Content version: v4•Public deck•Updated: 8/1/2026

Card preview (6)

#1
Front (Question)

Compare the lattice enthalpies of two (or three) compounds … Example: compare the lattice enthalpies of NaCl and MgCl2 In your answer: * Be specific about the ions, e.g. Na+ compared to Mg2+

Back (Answer)

• Mg2+ ion has a higher charge than the Na+ ion • Mg2+ ion is also smaller than the Na+ ion • Greater attraction between Mg2+ and Cl- ions • MgCl2 has a more exothermic lattice enthalpy

#2
Front (Question)

Example: compare the lattice enthalpies of KCl and CaO

Back (Answer)

• Ca2+ ion has a higher charge than the K+ ion • Ca2+ ion is smaller than the K+ ion • O2- ion has a higher charge than Cl- ion • O2- ion is smaller than Cl- ion • Much greater attraction between Ca2+ and O2- ions! • CaO has a much more exothermic lattice enthalpy

#3
Front (Question)

Example: compare the lattice enthalpies of MgS and Na2O

Back (Answer)

• Mg2+ ion has a higher charge than the Na+ ion • Mg2+ ion is smaller than the Na+ ion • O2- ion is smaller than S2 ion • Mg2+ attracts negative ions more strongly than Na+ • But O2- attracts positive ions more strongly than S2- • Cannot predict which lattice enthalpy is the most exothermic!

#4
Front (Question)

Compare the hydration enthalpies of two (or three) ions … Example: compare the hydration enthalpies of Na+ or K+ These are easier as you are only asked to compare ions, since the entha

Back (Answer)

• Na+ ion is smaller than K+ ion • Greater attraction between Na+ and H2O molecules • Na+ has a more exothermic hydration enthalpy

#5
Front (Question)

Example: compare the hydration enthalpies of Cl- or O2-

Back (Answer)

• O2- ion has a higher charge than the Cl- ion • O2- ion is also smaller than Cl- ion • Greater attraction between O2- and H2O molecules • O2- has a more exothermic hydration enthalpy

#6
Front (Question)

Why is it difficult to predict the difference in enthalpies of solution? Example: compare the enthalpies of solution of NaCl and MgCl2

Back (Answer)

• Mg2+ ion has a higher charge than the Na+ ion • Mg2+ ion is also smaller than the Na+ ion • Greater attraction between Mg2+ and Cl- ions • MgCl2 has a more exothermic lattice enthalpy • Also greater attraction between Mg2+ and H2O molecules • Mg2+ has a more exothermic hydration enthalpy • Difficult to predict whether lattice enthalpy or hydration enthalpy has the bigger effect