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).
