Question

Calculate molal elevation constant of water if 0.154 molal solution of a substance boils at 373.23 K.

[Given: Boiling point of water = 373.15 K]

Options

• 0.52 K kg mol⁻¹

• 0.66 K kg mol⁻¹

• 1.86 K kg mol⁻¹

• 2.53 K kg mol⁻¹

Answer 1

0.52 K kg mol⁻¹

Explanation:

∆T_b = K_b × m

∴ K_b = `(∆"T"_"b")/"m"`

= `("T"_"b" - "T"_"b"^0)/"m"`

= `(373.23  "K" - 373.15  "K")/(0.154  "kg mol"^-1)`

= `0.08/0.154` kg mol⁻¹

= 0.52 K kg mol⁻¹