The Molarity M of a solute in a solution is defined as:
M=moles of solution / kilograms of solvent
Mass %= (mass solute/mass solution)x100%
Assume 100g of solution
Find moles of solute
Mass solute = (mass %/100%)mass solution
=(36%/100)100g=36 gHCL
36 gHCL 1 mol HCL/36.458 gHCL= 0.987molHCL
36% HCL by mass 100 g solution
36g HCL 0.987Mol HCL
Molarity=moles solute/kg solvent
Find kg solvent
Mass solution = mass solute + mass solvent
Mass solvent = mass solution - mass solute
= 100 g-36=64 g solvent
64 g solvent = 1 kg solvent/1000 g solvent = 0,064 kg solute
Molarity= molHCL/0.064 kg solvent
=0.987/0.064
=15.42 mHCL