What is the molarity of 15g of LiCl dissolved in 500mL of water?

Molarity is the concentration of a given solution in moles per liters. It defines the number of moles contained in 1 liter of a solution.

In this case, 1 mole of lithium chloride contains 42.4 g

Therefore, 15 g contain 15/42.4 moles = 0.354 moles

0.354 moles are contained in 500 ml, thus 1 liter will have,

0.354 moles * 1000 / 500 = 0.707 moles

Thus, the molarity of LiCl = 0.707 M