Question

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How many molecules are in a sample of water, H2O, with a mass of 63.00 grams?

Answer 1

Answer: There are
`21.08* 10^(23)` molecules in 63.00 g of
`H_2O`

Step-by-step explanation:

According to avogadro's law, 1 mole of every substance occupies 22.4 L at STP and contains avogadro's number
`6.023* 10^(23)` of particles.

To calculate the moles, we use the equation:

`\text{Number of moles}=\frac{\text{Given mass}}{\text {Molar mass}}=(63.00g)/(18g/mol)=3.5moles`

1 mole of
`H_2O` contains =
`6.023* 10^(23)` molecules

Thus 3.5 moles of
`H_2O` contains =
`(6.023* 10^(23))/(1)* 3.5=21.08* 10^(23)` molecules.

There are
`21.08* 10^(23)` molecules in 63.00 g of
`H_2O`