Question

What is the molarity of 20% (w/v) H2SO4 solution?

(a) 0.51 M

(b) 1.02 M

(c) 4.08 M

(d) 2.04 M

I had been asked this question by my college director while I was bunking the class.

My query is from Expressing Concentration of Solutions topic in chapter Solutions of Chemistry – Class 12

Answer 1

Right option is (d) 2.04 M

The best I can explain: Given,

20% (w/v) means 20 g of H2SO4 is present in 100 mL (= 0.1L) of solution.

Data –

Moles of solute (H2SO4) = mass of solute/molar mass

Moles of solute, n = 20 g/(2 x 1 + 32 + 4 x 16) g/mole = 0.204 mole

Volume, V = 0.1 L

Molarity, M = moles of solute (n)/volume of solution (V)

M = 0.204 moles/0.1 L = 0.204 M.