Final answer:
CsF is likely to require the least amount of energy to separate one mole of solid into ions because it has a large sized cation, resulting in lower lattice energy compared to the other options that either have higher charges or smaller ions.
Step-by-step explanation:
To determine which of the listed substances requires the least energy to separate one mole of the solid into ions, we should consider the lattice energy of the compounds. Lattice energy is affected by the charge on the ions and the size of the ions.
Generally, the higher the charge and the smaller the ions, the greater the lattice energy, meaning more energy is needed to separate the ions.
Comparing the given substances:
- MgO - High lattice energy due to the doubly charged magnesium and oxygen ions.
- SrO - Similar to MgO but with a larger cation, SrO has slightly lesser lattice energy than MgO.
- KF - Has lower charges and larger sized ions compared to MgO and SrO, resulting in lower lattice energy.
- CsF - Larger cation than KF, therefore, even lower lattice energy due to the larger ionic size.
- MgF2 - Despite having a doubly charged magnesium ion, the larger size of fluoride compared to oxide would make its lattice energy lower than that of MgO.
Hence, among the options, CsF likely requires the least amount of energy to separate one mole of the solid into ions, due to having a large sized cation (Cs+) which reduces lattice energy.