PLEASE USE the BORN-MAYER equation and other data given below to calculate the l

Question

PLEASE USE the BORN-MAYER equation and other data given below to calculate the lattice enthalpy for calcium fluoride, CaF2, assuming it adopts the fluorite structure. r(Ca2+) = 100 pm r(F–) = 133 pm A(fluorite) = 2.52 d* = 34.5 pm

(ii) Using the value you calculated in (i), and the data below, calculate the enthalpy change upon dissolution of CaF2 in water. Listing any assumptions you make, predict whether calcium fluoride dissolves in water. H(hydration) Ca2+ = +1507 kJmol–1 H(hydration) F– = +505 kJmol–1

(iii) The radius of the Sr2+ ion is 118 pm. Would you expect SrF2 to be more or less soluble in water than CaF2? Explain your reasoning.

Explanation / Answer

1. CaF2----> Ca 2+ + 2F-

H= 1507+ 2*505= 1617KJmol-1

2. solubility = SrF2 > CaF2

cation with large size will high solubility w.r,t, to cation with less size.

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