Question

how do i calculate boiling point? (chemistry)

Answer 1

When water boils, the water temperature has reached a critical point where:

• The vapor pressure of the water is equal to the surrounding air pressure
• The liquid begins to convert to a gas (steam)
• The temperature of the water does not increase any more (it levels off)

Normal Boiling Point : As the atmospheric pressure varies with altitude and other condition ,the boiling points are reported at 1 atm.So,the normal boiling point of a liquid is the temperature at which the vapour pressure of the liqiud is 1 atm.

e.g. Normal boiling point of water = 100 c

Standard Boiling point : It is the temperature at which the vapour pressure of the liquid is 1 bar .

e.g. standard boiling point of water = 99.6 c

Experimentally, we know that the change in boiling point of the solvent above a solution from that of the pure solvent is directly proportional to the molal concentration of the solute:

Boiling Point Elevation

deltaT = K_bm

where:

delta T is the change in boiling point of the solvent,
        K_b is the molal boiling point elevation constant, and
        m is the molal concentration of the solute in the solution.