chemistry

I'm starting to learn about colligative properties and i want to know if there are different equations for boiling point elevation and freezing point depression? In the book they give me the equation: (delta)Tb= Kb times molality.
But my teacher gave us: delta Tb = Kb times # of ions x # of moles.
(This is for boiling point elevation)
Which one is correct?

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asked by jenny
  1. Yes and no.
    The general formula for the boiling point elevation is delta T = i*Kb*m but text books often omit the i(the number of particles) since covalent compounds have i = 1. The book is right, in a limited sense, but your teacher is right in all situations. For freezing point depression,
    delta T = i*Kf*m

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    posted by DrBob222

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