What is the molarity of a concentrated hbr solution if the solution is 27.7% hbr by mass and has a density of 1.24 g/ml

 
         M = No.of moles of solute / Volume of solution in litres
  HBr: H = 1 x 1 = 1       Br = 1 x 80   
             Molar mass : 81 g / mol
  a.  n = 27.7% / 100 =0.277 g / (81 g / mol) = 0.0034 mol
       
       density = 1.24 g/ml ; D= m / v
               
  b.   65.32 ml x 1 L / 1000 mL = 0.065 L

    
   c. M= n / V
          = 0.0034 mol / 0.065 L
       M= 0.052 mol / L

The molarity of the concentrated HBr solution is 0.052 mol/L