Question

The normal boiling point of a certain liquid X is 130.9 °C, but when 19.9 g of urea (NH2) CO are dissolved in 200. g of X, it is found that the solution boils at 134.1 °C instead. Use this information to calculate the molal boiling point elevation constant K, of X. Be sure your answer has the correct number of significant digits x 1 ℃.mol -kg

Answer 1

Answer:

K = 1.93 °C/m

Explanation:

This question can be solved by formula of elevation of boiling point.

Boiling T° of solution - Boiling T° of pure solvent = K . m . i

Our solute is urea.

Our solvent is X.

We convert mass of urea to moles: 19.9 g . 1 mol / 60.06g = 0.331 mol

We convert g of solute to kg = 200 g . 1 kg/ 1000g = 0.2kg

m = molality → moles of solute / kg of solvent

m = 0.331 mol / 0.2 kg = 1.66 m

As urea is an organic compound, no ions will be formed.

i = 1 (a non ionizing compound)

Let's replace data in formula:

134,1°C - 130.9°C = K . 1.66 m . 1

3.2 °C / 1.66 m = K

K = 1.93 °C/m