Question

53. Order of solubility of alkali metal fluorides in
water is
1) CsF<NaF < KF < LiF
2) LiF<KF <NaF < CsF
3) LiF<NaF< KF< CsF
4) CsF< KF <NaF< LiF​

Answer 1

Answer:

3) LiF<NaF<KF<CsF

Explanation:

$solubility \: \alpha \: hydration \: enthalpy \\ \\ hydration \: enthalpy \: \alpha \ \: \frac{1}{lattice \: enthalpy} \\ \\ by \: coulomb \: law \\ \\ \: force(lattice \: enthalpy) \: \alpha \: \frac{1}{ {distance}^{2} }$

Now, Distance is minimum between Li and F and maximum between Cs and F. Hence, LiF has highest lattice enthalpy and lowest hydration enthalpy and CsF has lowest lattice enthalpy and highest hydration enthalpy (solubility).

Hope you got it,

cheers!