If 1.0 mL of 6.0 HCl is added to 499 mL of water to give exactly a 500 mL solution, what is the molarity of the solution

Molarity = Moles/Liters. First, convert all ml to Liters by moving the decimal 3 places to the left and then calculate:

.001 L HCl x 6M/L HCl /.5 Liters of solution=0.012 Moles per Liter aka molarity