acetone is a common solvent and has a density of 0.7899 g/ml. What volume of acetone, in mL has a mass of 31.8 g?

Question

I need help breaking this down so that I can understand how to work it out. 

Answer 1

Density is mass per volume, so in this case, it is 0.7899 g/ml

You can set up a proportion like 0.7899 g/31.8 g = 1 ml/x ml

x = 40.26 ml = 40.3 ml (to 3 significant figures)

 

Looking at it another way, each ml has a mass of 0.7899 g, so how many mls will it take to get 31.8 g?

(x ml)(0.7899 g/ml) = 31.8 g

x = 31.8 g/0.7899 g/ml = 40.3 ml