Question

The density of a 50% solution of naoh is 1.525 g/ml. what volume of a solution that is 50% by weight naoh is required to make 0.4 liter of 0.1m naoh solution?

Answer 1

We consider that the 50% given in this item is by volume. Molarity is the unit of concentration that takes into account the number of moles of the solute and the number of moles of the substance.

      number of moles of NaOH = (0.1 moles / L)(0.4 L)
                      n = 0.04 moles of NaOH

If we are to take the basis of 1 mL of 50% NaOH solution, 
  
                  (1 mL solution)(1.525 g/mL)(0.50) = 0.7625 g
The number of moles is,
                  0.7625 g NaOH x (1 mol / 40 g) = 0.01906 moles of NaOH

                volume of solution required = (0.04 moles of NaOH)(1 mL solution / 0.01906 moles of NaOH)
                 
                 volume of solution required = 2.09 mL

Answer: 2.09 mL