a stock solution of perchloric acid is 75.5% perchloric acid and has a density of 1.67g/ml. What is the molarity of the solution?

Answer 1

75,5% (w/w??) = 75.5 g HClO4/100 g soln
mols HClO4 = grams/molar mass = ?
Use density to convert 100 g soln to volume (in mL) and convert to L.
Then M = mols/L soln.