Problem I:
Calculate the molality and mol fraction 
  of HCl for a solution which has a mass percent of 37.1 %. 
Summary:
Step 1: Assume amounts of solute and solvent in terms of the 
  concentration definition the solution is defined. 
  For example if the concentration of the solution is given in 
    weight %, assume 100 grams of solution than determine the mass of solute and 
    solvent.
Step 2: Convert the grams of solute to mols, convert the grams 
  of solvent to kilograms, then calculate the molality of the solution.
Step 3: Convert the grams of solvent to mols, use mols of solute 
  from Step 2, then calculate the mol fraction of the solution.