Question

what is the number of water molecules contained in a drop of water weighing 0.06 gram

Answer 1

Number of moles = given mass/molar mass
Given mass = 0.06 g
Molar mass of water = 18g/mol
Numbe of moles = 0.06/18
= 0.00333 moles
1 mol = 6.022 ×× 1023 molecules 
0.00333 moles = 0.00333××6.022 ×× 1023 molecules 
= 0.02 ×× 10 23 molecules 
Hence, 0.06 g of water has 0.02 ×× 10 23 molecules 

Answer 2

no. water of molecules = mole × NA

= 0.06/18 × 6.02 × 10^23

= 0.02005 × 10^23

= 20.05 × 10^20 molecules of water

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