# Calculating boiling point of a solution

What is the boiling point of an aqueous solution that has a vapor pressure of $$23.0~\text{Torr}$$ at $$25~^\circ\text{C}$$?

$$(P^\circ_{\ce{H2O}}=23.78~\text{Torr};~K_\mathrm b= 0.512~^\circ\mathrm{C\ kg/mol})$$

To solve this I used the equation $$\Delta T_\mathrm b =m\times K_\mathrm b$$. I calculated a molality of $$1.88247\ \mathrm{mol/kg}$$ which I then used to calculate a boiling point of $$-0.9638\ \mathrm{^\circ C}$$. This answer is apparently wrong and I don't understand why.