Mixture A is formed using KCl and H2O and mixture B is formed using MgCl2 and H2O. If the two mixtures have the same molality, which of the following statements would be true about the boiling point of the mixtures?
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Correct Answer: B. Mixture A would have a lower boiling point
The two mixtures have the same concentration a.k.a. molality. However, they do have differing ionic solutes. Mixture A has an ionic solute that would dissociate to form two ions (K+ and Cl–) whereas Mixture B has an ionic solute that forms three ions (Mg2+ and 2Cl–). In the equation:
āT(boiling) = m x Kb x i, the āIā or vant Hoff factor would be the only variable. The higher the vant Hoff factor, the greater the effect on the boiling point and/or freezing point. The von hoff factor for Mixture A is 2, but for Mixture B is 3. Therefore, Mixture B would have the greater affect on the boiling point, making it higher than normal. Between the two mixtures, B would have a higher boiling point than mixture A.
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