Question

the percentage (by weight) of sodium hydroxide in a 1.26 molal NaOH solution is

Answer 1

1.26 molal naoh solution means 1.26 molals of naoh in 1 kg of water

hence mass of naoh = number of moles x molar mass = 1.26 * 40 = 50.4 g

mass of water = 1000 kg mass of solution = 1000+50.4 = 1050.4 %by mass of naoh = [mass of naoh / mass of solution ] *100                               = 50.4 / 1050.4 * 100                               = 4.79 ans