We need the quotient, #"moles of solute"/"volume of solution"#
In #100*g# of SOLUTION there are #17*g# of #HCl# solute; the volume of this solution is #"Mass"/("density"(rho))=(100*g)/(1.21*g*mL^-1)# #=# #82.6*mL#.
Given this we can calculation the concentration with respect to molarity:
#"Concentration"=((17*g)/(36.46*g*mol^-1))/(82.6*mLxx10^-3*mL*L^-1)~=6.0*mol*L^-1#
The most concentrated hydrochloric acid you can buy#("mass"/"mass")xx100%# is approx. 36%. This corresponds to a concentration of approx. #12.0*mol*L^-1#. Note that all I have done here is approach the problem dimensionally, and most of the problems you encounter as an undergrad may be solved by this method.
Also note that pure #HCl# would be a room temperature gas #("boiling point"=-85.5# #""^@C)#.
