If 1 mL of H2O contains 20 drops, then no. of molecules in a drop of water are

Volume of 20 drops = 1ml⇒ Volume of 1 drop= 120ml Mass of water = 120g [since density= 1g/cm3]∴ Moles of water =120×118​= 0.0518∴ Number of molecules = 0.0518NA=0.0518×6.023×1023= 1.673×1021 molecules