How many moles of #HCl# are in 75.0 mL of 0.200 M solution?
These questions can easily be resolved using the relationship that concentration (or molarity) m = no. of moles / no. of litres.
In this case, simply rearrange for no. of moles.
No. of moles = molarity x no. of litres = 0.2 x (75/1000) = 0.015 mol.