Question

A solution of H2SO4 with a molal concentration of 5.25m has a density of 1.266 g/ml. what is the molar concentration of this solution?

Answer 1

molal concentration is expressed as number of moles of solute over kg solvent while molar concentration is expressed as moles solute over liter solution.

In this case, on a basis of 1 kg water, there are 5.25 moles * (98 g/mol) = 514.5 grams H2SO4

The liters solution is equal to
V = (514.5 g + 1000 g H2O) /(ml/1.266g) /1000 = 1.1927 L

Hence the molarity is
5.25 moles/1.1927 L or 4.40 molar.

Answer 2

so first find the moles of the H₂SO₄: Mass = Moles x RFM
so mass = 5.25 x 98 = 514.5g of H₂SO₄

so to find how many Liters of solution use:

Volume = Density x Grams of solute (per kg +1000)

density = 1.266 x 514.5 +1000 = 1917.357kg/l

now use equation: Conc. = Moles / Volume of solution to find the conc.
Conc. = 5.25 x 1917.357 = 4.39Mol⁻¹
Hope that helps