What do I do next?

[bestsmilez]

---

Members don't see this ad.

I am having some major problem continuing this problem:

What is the molality of 85% phosphoric acid, H3PO4, if the density of the solution is 1.70 g/ml?

all i know so far is that there is 85g of the acid and 15g of the solvent. Molality is moles of solute / kg of solvent...I dont know where to incorporate the density of the solution to set up of the problem..I dont understand achiever's explanation..Help pls. Thanks in advance..

 

[jleefe]

As you said, molality is moles/kg solvent. 85% solution means that, for every 100g of H2O, there is 85g of H3PO4; Density of 1.70g/mL means 1.70g H2O per mL of solution, so:

85g H3PO4/100g H2O x 1.70g H2O/1mL solution x 1mol H3PO4/98g H3PO4 x 1000mL/1kg solution = 14.7moles H3PO4/kg solution