Calculate molality of 5.01 M (molar) NaOH solution if density of solution is 1.5g/ml. Use log table and show logs used.

Answer 1

If the solution is stated to be 5.01 M (molar), then there are no calculations to find the molarity. It is given to you as 5.01 molar. Are you sure that is the exact question? Are you asking about molality, and not molarity maybe?

EDIT: Now that you told us it is the molality that should be calculated, it can be done as follows:

molality = moles of NaOH per kg of water.

Since molarity = 5.01 M, there would be 5.01 moles/liter of solution

1L = 1000 ml x 1.5 g/ml = 1500g

5.01 moles NaOH = 5.01 moles x 39.997 g/mole = 200.38 g NaOH

g H2O = 1500 g - 200.38 = 1299.62 g H2O

molality = moles NaOH/kg H2O = 5.01moles/1.2996 kg = 3.9 m (to 2 significant figures).

(note: not sure why they asked you to use logs)