What is the modularity of 750 ml of nacl solution that contains 21.04 g of nacl

Molar mass of NaCl = 58.44 g/mol

Number of moles :

n = mass / molar mass

n = 21.04 / 58.44

n = 0.36002 moles

Volume = 750 mL in liters 750 / 1000 = 0.75 L

Molarity :

M = number of moles / Volume in liters

M = 0.36002 / 0.75 

M ≈ 0,4800 mol/L⁻¹

hope this helps!