Question

Molarity of 720 gm of water

Answer 1

Molarity = weight by molecular weight *100 by 1000.. That gives you 4 M.

Answer 2

Molarity = No. of moles of solute/ Vol. of solvent in litre
No. of moles = given mass/ molar mass
=720/18 = 40
Molarity = 40 mol/L