Question

1.)An aqueous solution is 34.0% H3PO4 by mass and has a density of 1.207 g/mL. What is the molarity of the solution? AND what is the molality?

Answer 1

density = 1.20 g/mL so 1000 mL has a mass of
1.20 x 1000 = 1200 grams
How much of that is H3PO4? 34.0%.
1200 x 0.34 = 408 g.
How many moles is that?
408/98 = 4 something. You do it exactly. That is 4 something moles in 1 L so Molarity = 4 something.

Molality:
1000 mL has a mass of 1200 grams and 408 of that is H3PO4.
You know the number of moles from above. But the g solvent is 1200-408 = ??. Change that to kg and m = moles/kg.
Close to 5 m. You do it exactly.

Answer 2

thank you