solution A contains 1 mole of sodium chloride in 1 litre of water. solution b contains 1 mole of potassium chloride in 1 litre of water. both solutions are heated and the boiling point is measured. which of the following statements is correct?
A: solution a has a higher boiling point
B: solution B has a higher boiling point
C: both solutions will have the same boiling point
D more information is needed
the answer key says that it should be C, both have the same since they both dissolve into 2 ions. but I thought it would be B because potassium chlorate will have a higher LDF causing a higher boiling point than solution A. i am missing a point here but I couldn’t find what.
Ionic compounds dissociate into separate ions when dissolved in water. The details are pretty complicated because you need to know about the Van Hoff factors. The key point is that the same number of MOLES are used. There are two ions in each solution both with the same magnitude of charge. (The Van Hoff factor of both solutions are 2 - adding up the magnitudes of ion charge)
NaCl - Na+1 and Cl-1
KCl- K+1 and Cl+1
The Van Hoff factor is close to the ideal factor making them ideal solutions. ideal solutions of EQUIMOLAR NaCl and KCl would have identical boiling points.
Of course if the mass was the same, the same mass of KCl has fewer ions, due to the higher atomic mass of K, so will have a lower concentration. Since the boiling point elevation is directly proportional to the ion concentration, this will lead to a lower boiling point than NaCl.
Maybe just remember that if its the same number of moles, the boiling points would be almost identical. Since the reason itself is more complicated :))
Hope this helps!
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