Question

what is the molecular mass of an organic compound if 16.00g of the compound is dissolved in 225.0g carbon tetrachloride raises the boiling point to 85.36°c​

Answer 1

Given info : 16g of an unknown organic compound is dissolved in 225g carbon tetrachloride raises the boiling point to 85.36° C.

To find : The molecular mass of the organic compound is...

solution : ebulioscopic constant for CCl4, Kb = 5.03 °C kg mol¯¹ [ experimentally ]

boiling point of CCl4 = 76.72°C

so change in temperature, ∆Tb = 85.36 - 76.72 = 8.64°C

mass of solute (organic compound) = 16g

let molar mass of solute is M

so molality = no of moles of solute per kg of solvent

= (16/M)/(225/1000)

= 16000/225M

= 640/9M

now using formula, ∆Tb = Kb × m

⇒8.64 = 5.03 × 640/9M

⇒M = 5.03 × 640/(9 × 8.64)

= 41.4 g/mol

Therefore the molar mass of organic compound is 41.4 g/mol