Question

A perchloric acid solution is composed of 168.75 g of perchloric acid and 81.25 mL of pure water. What is the percent by mass of the perchloric acid solution? The density of
water is 1.000 g/mL.

When I did this part I got 67.5%
But, I am having trouble with the secind part.

The density of the above perchloric acid solution is 1.138 g/mL. What is the molarity of the perchloric acid solution?

I know molarity is moles solute/liter of solution, but how do i find that from %mass? please help if you can!! Thanks!

Answer 1

You have 67.5 g HClO4 in 100 g soln.
Convert 67.5 g HClO4 to moles.
Using the density, convert 100 g soln to mL, then M = moles/L.

Answer 2

:) Thanks you so much! :)