Molarity is the number of moles of solute per kilogram of solvent.
Molarity of Water
Molarity = Number of moles of solute per litre of solution in molar concentration
M = no of moles / volume
Mole = mass/molar mass = 1000/18= 55.56 mol
1l of water = 1000mL = 1Kg
Density = 1000kg/m3
therefore Molarity = 55.56mol/1L = 55.56mol/L