Question

An aqueous solution of phosphoric acid, H3PO4, contains 285 g H3PO4 in 400 mL solution, and has a density of 1.35 g/mL. Calculate

a. the weight % H3PO4 in this solution.

b. the concentration in mol/L of this solution

Answer 1

If it contains 285 g in 400 mL how much is in 1 L?
285 x (1000/400) = 712.5 g H3PO4 in 1 L.

How much does 1 L weigh? It has a mass of
1.35 g/mL x 1000 mL = 1350 grams.

So the mass% is (mass H3PO4/mass solution)*100 = ??

How many moles H3PO4 in that 712.5 g H3PO4. That is moles = grams/molar mass.
Then M = moles/L of solution and that 712.5 g IS for 1 L of solution.
Check my work.

Answer 2

53.54