Question

4. (6 points) The boiling point of an aqueous solution composed of 15.2 g of an unknown molecular compound in 78.g of water is 108.3. C. What is the molar mass of the unknown compound? Kh for water is 5.21 °C/m. ivant noff factor ^ Th= i kbm AT6= boiling point elevat AT6= boiling point elevation met toolrood Kosmoral boiling point elevation constant (5.210/m! m= solution morarity. MW=mol = 15.2g 108.30 = 1(5.2104m) 20.78 = 48x10 m 108.3 108.3

Answer 1

let molar mass of unknown compound = M g / mole.

mole of unknown compound (15.2 / M) mole.

molality = (15.2 / M) mole / 0.078 Kg = (194.87 / M) mole / Kg

we know,

delta Tb = i * Kb * m

or

(108.3 - 100) = 1 * 5.21 *  (194.87 / M)

or

M = 122.3 g / mole.

thus

molar mass of unknown compound is 122.3 g / mole.