ICSE Class 10 Answered

Snowflakes are made of water (H₂O).The mass of 1 mole of water is calculated as follows:

Mass of H₂O = 2(mass of H) + mass of O

Mass of H₂O =2 (1.01g)   + 16.00g

Mass of H₂O = 2.02g + 16.00g

Mass of H₂O = 18.02 g

One mole of H₂O contains 6.022×10²³ molecules of H₂O (Avogadro’s number)

Therefore, 1 g of H₂O contains = (6.022×10²³ H₂O molecules) / (18.02g)

There are 3.34×10²² H₂O molecules in 1g of H₂O.

So snowflake weighing 1 mg contains = (3.34×10²² molecules) / (1000)

Hence, there are 3.34×10¹⁹ H₂O  molecules in 1 mg snowflake.