posted by nancy on .
I have a 0.25 m aquaeous solution of HCL. It's density is 1.05 g/ml. WHat is the % by mass (m/m) of this solution? What is the molarity of the solution?
m = # mols/kg solvent.
We have 0.25 m so we must have 0.25 x 36.5 g/mol HCl = 9.125 g HCl/1000 g solvent. The total mass of the solution, then, is 1000 g solvent + 9.125 g HCl = 1009.125 g.
percent by mass = [9.125/1009.125]x100 = ?? and round to the appropriate number of places.
Molarity = # mols/liter of solution.
mass of 1 L of solution = 1.05 g/mL x 1000 mL = 1050 grams.
How much of that is HCl?
1050 g x (%/100) = grams HCl.
grams HCl/molar mass HCl = mols HCl/L which is Molarity.
Check my thinking. Check my numbers carefully.