Question

calculate number of atoms having 20 gram of water also calculate number of moles

Answer 1

Molar mass of water = H2O = 18.
Number of moles = Given mass / Molar mass.
= 20/18 = 1.11 moles.

Number of moles = Number of atoms ÷ Avagardo's number.
1.11 = Number of atoms ÷( 6.022 × 10^23)
Number of atoms = 1.11 × 6.022 × 10 ^23
Number of atoms = 6.68442 × 10 ^23

Hope it helps !! ;-)