Which sample contains the most concentrated solution of hydrochloric acid (HCl) ?

A.) 300mL of 1.00M HCl

B.) 50mL of 1.45M HCl

C.) 800mL of 2.00M HCl

D.) 2.00L of 0.90M HCl

The unit of concentration in all the data is M. That is molarity or number of moles of solute per liter of solution.

The amount of sample or volume does not varies the concentration of the solution.

Then you only must compare the molarities and the greater the molarity (moles/liter) the greater the concentration or the more is concentrated the solution.

In this case the order is 0.90 M < 1.00 M < 1.45 M < 2.00 M.

And so, we get to the conclusion that the option C. is the most concentrated solution: 800 mL of 2.00 HCl.