A certain substance has a normal boiling point of and a molal boiling point elev

Question

A certain substance has a normal boiling point of and a molal boiling point elevation constant... (see image) Please round to appropriate significant digits.

A certain substance X has a normal boiling point of 124.2 °C and a molal boiling point elevation constant K,-06-0C-kg-mol ·A solution is prepared by dissolving some urea ((N112)CO) in 650. g ofl. This solution boils at 124.7 oC, Calculate the mass of urea that was dissolved. Be sure your answer has the correct number of significant digits. 31.48 g

Explanation / Answer

According to colligative property elevation in boiling point,

T - T0 = i * Kb * molality of solution

T = boiling point of the solution = 124.7 0C

T0 = boiling point of the pure solvent = 124.2 0C

Kb = elevation of boiling constant = 0.62 0C.Kg/mol

molality = maas of solute/molar mass of solute * 1000/ mass of solvent in g

i = vant hoff's factor

since urea is soluble inwater and donot dissociate into ions so i = 1

By substituting all the values,

T - T0 = i * Kb * molality of solution

124.7 - 124.2 = 1 * 0.62 * m/60*1000/650

m = 31.45 g of urea is dissolved.

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