Question

If the density of methanol is 0.793 kg L^–1, what is its volume needed for making 2.5 L of its 0.25 M solution?

Answer 1

Molar mass of methanol (CH₃OH) = (1 × 12) + (4 × 1) + (1 × 16)

= 32 g mol^–1

= 0.032 kg mol^–1

Molarity of methanol solution `=(0.793" kg L"^-1)/(0.032" kg mol"^-1)`

= 24.78 mol L^–1

(Since density is mass per unit volume)

Applying,

M₁V₁ = M₂V₂

(Given solution) (Solution to be prepared)

(24.78 mol L^–1) V₁ = (2.5 L) (0.25 mol L^–1)

V₁ = 0.0252 L

V₁ = 25.22 mL