Question

How many molecules of H2O are there in 1.0 g of H2O?

Answer 1

Avogadro's number represents the number of units in one mole of any substance. This has the value of 6.022 x 10^23 units / mole. This number can be used to convert the number of atoms or molecules into number of moles. This will be used for the conversion to be done.

1.0 g H2O ( 1 mol / 18.02 g ) ( 6.022 x 10^23 molecules / mol) = 3.3 x 10^22 molecules

Answer 2

Answer : The number of molecules of $H_2O$ are, $3.31\times 10^{22}$

Explanation : Given,

Mass of $H_2O$ = 1.0 g

Molar mass of $H_2O$ = 18 g/mole

First we have to calculate the moles of $H_2O$.

$\text{Moles of }H_2O=\frac{\text{Mass of }H_2O}{\text{Molar mass of }H_2O}=\frac{1.0g}{18g/mole}=0.055moles$

Now we have to calculate the number of molecules of $H_2O$.

As, 1 mole of $H_2O$ contains $6.022\times 10^{23}$ number of $H_2O$ molecules.

So, 0.055 mole of $H_2O$ contains $0.055\times 6.022\times 10^{23}=3.31\times 10^{22}$ number of $H_2O$ molecules.

Therefore, the number of molecules of $H_2O$ are, $3.31\times 10^{22}$