In: Chemistry
An aqueous solution of glycerin, 7% by weight, is prepared. The solution is found to have a density of 1.0149 g/mL. The density of pure glycerin (MW=92.0473) is 1.2609 g/mL. What is the molarity and molality concentration of the solution?
Solution :-
Lets assume we have 100 ml solution (0.100 L)
then mass of solution = volume * density
= 100 ml * 1.0149 g per ml
= 101.49 g
now lets find mass of glycerin
101.49 g * 7 % glycerin / 100 % = 7.1043 g
now lets calculate moles of glycerin
moles = mass / molar mass
moles of glycerin = 7.1043 g / 92.0473 g per mol
= 0.07718 mol glycerin
Now lets calculate the molarity
molarity = moles / volume in liter
= 0.077181 mol / 0.100 L
= 0.77181 M
now lets calculate the molality
molality = moles / kg solvent
mass of water = 101.49 g - 7.1043 g = 94.3857 g = 0.0943857 kg
molality = 0.7718 mol / 0.0943857 kg
=0.81771 m