Question

Which of the following ions will contribute most to elevating the boiling point of H₂O? A) Na+ B)K+ C) Ca₂+ D) All will contribute equally O F G H J

Answer 1

The
`Ca^{2+` ion will elevate the boiling point of
`H_2O` the most because it dissociates to give three ions per formula unit, leading to a higher elevation compared to Na+ and K+ which only produce two ions per formula unit.

Step-by-step explanation:

The ion that will contribute most to elevating the boiling point of H₂O among Na+, K+, and
`Ca^{2+` is
`Ca^{2+`. This is because the boiling point elevation of a solution is proportional to the molal concentration of the dissolved particles (ions in this case), a concept known as the colligative properties of solutions.

Since each mole of CaCl₂ dissociates into three ions (one
`Ca^{2+` and two Cl−), it will contribute more to the elevation of the boiling point compared to NaCl and KCl, which dissociate into two ions each.