How much solid solute (in grams) would need to be measured out if you wanted to create a 1.25M CuSO4 solution with a volume of 100.0mL?

Question

How much solid solute (in grams) would need to be measured out if you wanted to create a 1.25M CuSO₄ solution with a volume of 100.0mL?

Answer 1

So, Amanda...

What does 1.25 M actually mean? It means 1.25 mols of solute in 1 liter of solution.

We don't have 1 liter of solution as we have only 100.0 mls of solution. This is 0.1 liters (100 ml x 1 L / 1000 mls = 0.1 L)

So, instead of needed 1.25 mols solute, we need only 1/10 of that or 0.125 mols.

Another way to look at this is 1.25 mols / L x 0.1 L = 0.125 mols needed

The molar mass of CuSO₄ is 159.6 g / mol

Thus we need 0.125 mols x 159.6 g /mol = 19.95 g CuSO₄ = 20.0 g (3 sig. figs.)