m= 2.06
molality is m = moles/kg
if you look at the periodic table the mass of HCl is 36.458 rounded to 36.5
divide the 19.5g by the mass (36.5) and you’ll get 0.53
next, you convert g to kg so you divide by 1,000. 257/1,000 = 0.257
you plug those two answers into the equation > m= 0.53 mol HCl/ 0.257kg H20
the answer will be 2.06 when you divide and there’s how you get the molality.
remember, HCl is the solute and H20 is the solvent.