Question

A solute is a strong electrolyte that ionizes into 2 ions. What is the molar mass of this solute if 30.76 grams added to exactly 1 kg of solvent change the boiling point by 0.899 °C? (The Kb value for this solute is 0.511 °C/m).

Answer 1

Answer:

34.9 g/mol is the molar mass for this solute

Explanation:

Formula for boiling point elevation: ΔT = Kb . m . i

ΔT = Temperatures 's difference between pure solvent and solution → 0.899°C

Kb = Ebullioscopic constant → 0.511°C/m

m = molality (moles of solute/1kg of solvent)

i = 2 → The solute is a strong electrolyte that ionizes into 2 ions

For example: AB ⇒ A⁺  +  B⁻

Let's replace → 0.899°C = 0.511 °C/m . m . 2

0.899°C / 0.511 m/°C . 2 = m → 0.879 molal

This moles corresponds to 1 kg of solvent. Let's determine the molar mass

Molar mass (g/mol) → 30.76 g / 0.879 mol = 34.9 g/mol