Question

6 g of NaOH are dissolved in 200 cm³ of water. What is the relation between molarity and normality of the solution thus obtained?

Answer 1

Given: Mass of NaOH = 6 g

Volume of solution = 200 cm³ = 0.2 L

Molar mass of NaOH = 40 g/mol

NaOH is a monobasic base (provides 1 OH⁻ ion per molecule).

Molarity (M) = `"Given mass"/("Molar mass" xx "Volume in litres")`

M = `6/(40 xx 0.2)`

M = `6/8`

Molarity (M) = 0.75 M

For NaOH, Normality = Molarity × Basicity

Since NaOH is monobasic, Basicity = 1

Normality (N) = 0.75 × 1

Normality (N) = 0.75

i.e., Molarity = Normality

Because NaOH is a monobasic base, molarity and normality are equal for this solution.