Question

Calculate the number of water molecules present in one drop of water which weighs
0.18 g.

Answer 1

First,find the number of moles:

for that, apply the relation between mass and number of moles (n=m/M) while n is the number of moles and M is the molar mass of the entity.

The molar mass of water (H2O) is 18g/mol (M (O) =16. M (H )=1).

So the number of moles in this drop of water is 0.01mol.

To find the number of molecules in this drop of water you multiply the number of moles that is 0.01 by the Avogadro constant is known as NA=6.02*10^23.

So that makes 6.02*10^21 molecules of water

Answer 2

Hi mate

Question

Calculate the number of water molecules present in one drop of water which weights 0.18g.

Solution

Mass of water = 0.18g

$No \: Of \: Mole = Mass \div Molar \: Mass$

= 0.18/18

= 0.01 Mole

$No.of.molecules = No.of.Moles × Avagadros Number$

= 0.01 × 6.023 × 10²³

= 0.06023 ×10²³

= 6.023 × 10²¹

Therefore, 6.023 × 10²¹ molecules is your answer.

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