Question

calcuate the number of atoms presents in 90g of H2O​

Answer 1

Answer:

For water we have 2 hydrogen atoms and one oxygen, so the atomic weight of water is 1+1+16=18, so a mole of water is 18 grams. We have 90g of water so we have 90/18 = 5 moles of water.

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Answer 2

Answer:

the atomicity of a molecule of H2O = 2(1u) +1(16u) = 18u

We have 90g of water so we have 90/18 = 5 molecules of water

so,

5 x 18 = 90u