Question

a 12.5% (w/w) nicl2 (129.61g/mol) solution has a density of 1.149 g/ml. calculate the molar solution of nicl2

Answer 1

12.5 w/w% means there is 12.5 g of NiCl2 per 100 g ofsolution (i.e. 100 g of (solute + solvent)). The density of thesolution is 1.149 g/mL, so the volumeof solution corresponding to100 g is:
volume = 100 g / 1.148 g/mL = 87.11 mL
So a 12.5% w/w solution of NiCl2 contains 12.5 g ofNiCl2 per 87.11 mL of solution. We have volume, so nowwe just need to calculate moles:
moles = mass / molar mass
= 12.5 g / 129.61 g/mol
= 0.09644 mol
So the concentration is:
concentration = moles / volume
= 0.09644 mol / 0.08711 L
= 1.11 M