Question

Calculate the molarity of 80.0 ml of a solution that is 0.92 % by mass nacl. assume the density of the solution is the same as pure water.

Answer 1

We are given the volume of the solution which is 80 mL or 0.08 L and the density which is equal to water, density = 1 kg / L.  Therefore calculate total mass:

total mass = (1 kg / L) * (0.08 L) = 0.08 kg = 80 g

 

So the mass of NaCl is:

mass NaCl = 0.0092 * 80 g = 0.736 g

The molar mass of NaCl is 58.44 g/mol, so the number of moles is:

moles NaCl = 0.736 g / (58.44 g/mol) = 0.0126 mol

 

SO the molarity is mol / L:

Molarity = 0.0126 mol / 0.08 L = 0.157 mol/L = 0.157 M