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taskmasters
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 : The number of molecules of [tex]H_2O[/tex] are, [tex]3.31\times 10^{22}[/tex]

Explanation : Given,

Mass of [tex]H_2O[/tex] = 1.0 g

Molar mass of [tex]H_2O[/tex] = 18 g/mole

First we have to calculate the moles of [tex]H_2O[/tex].

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

Now we have to calculate the number of molecules of [tex]H_2O[/tex].

As, 1 mole of [tex]H_2O[/tex] contains [tex]6.022\times 10^{23}[/tex] number of [tex]H_2O[/tex] molecules.

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

Therefore, the number of molecules of [tex]H_2O[/tex] are, [tex]3.31\times 10^{22}[/tex]