An aqueous solution of NaOH is marked as 20 % (w/w) and has a density of 1.2 g mL ⁻¹ at 298 K. Which of the following statements regarding this solution is incorrect ? (Molar mass of NaOH = 40 g mol ⁻¹ )

Step-by-step solution

Let us consider 100 g of the 20 % (w/w) aqueous NaOH solution. Mass of NaOH = 20 g Mass of water (solvent) = 100 - 20 = 80 g = 0.08 kg Moles of NaOH = 20 40 = 0.5 mol Molality (m) = Moles of solute Mass of solvent in kg = 0.5 0.08 = 6.25 m. This statement is correct. Volume of 100 g solution = Mass Density = 100 1.2 mL = 100 1200 L = 1 12 L. Molarity (M) = Moles of solute Volume of solution in L = 0.5 1/12 = 6.0 M. This statement is correct. For 1 L ( 1000 mL) of the solution: Mass of 1 L solution = Volume Density