Question

How do you find the mass of a solution if you have 1L of 2.5 M MgCl2.

I have determined how many moles are present in MgCl2 which was 2.5 and how grams are present which came out to be 238.025g

Now I'm asked "What is the mass of the solution and the mass of the solvent(water)? (Assume the solution has a density of 1.00g/mL)

Answer 1

With a density of 1.00 g/mL, then 1000 mL has a mass of 1.00 g/mL x 1000 mL = 1,000 grams. 238.025 g is MgCl2, 1000-238.025 = mass solvent.

Answer 2

To find the moles of solvent present, would you divide the mass the solvent by 18.02g/mol?

I am given this: MM=18.02g/mol

Answer 3

Sorry the 18.02 is for water.

Answer 4

Yes, moles = grams/molar mass.

Answer 5

Ok now I have to find the mole fraction of the solvent.

I know the formula, which is the moles of a substance/ total moles of solution.

Is the moles of the substance the number we just obtained? And which is the "total" moles of solution?

Answer 6

XMgCl2 = moles MgCl2/(moles MgCl2 + moles H2O)

XH2O = moles H2O/(moles MgCl2 + mols H2O)