How many water molecules in a 0.90⋅g mass of water?

3 Answers
kceylan · Stefan V.
Oct 25, 2017

3.01×1022 molecules.

Explanation:

The mass of one mole of water is 18 g. Therefore, 0.9 g of water is

0.9 g18 g/mol=0.05 moles

of water. One mole of water contains Avagadro's constant, ie, 6.022×1023 molecules of water, therefore, 0.05 moles of water contain

0.05 mol×6.02223molec.1 mol=3.01×1022 molecules

anor277
Oct 25, 2017

We find the molar quantity.....and get number of water molecules =3.01×1022...

Explanation:

Moles of water=0.9⋅g18.01⋅g⋅mol−1=0.050⋅mol

And we know that there are 6.022×1023 molecules in one mole of any substance.....

And so we take the product......

0.050⋅mol×6.022×1023⋅mol−1=3.01×1022 water molecules. (And thus the product gives a dimensionless number as required....)

(i) how many oxygen atoms in this molar quantity; and (ii) how many hydrogen atoms......?

Saliha
Oct 25, 2017

30.1 x 1021mlcs

Explanation:

Massofwater(H2O) =0.9grams

Molarmassof(H2O) =1.008 x 2 + 16
=18.016gmol−

** Number of molecules ** = Mass in grams/Molar mass x NA

=0.918.016 x 6.02 x 1023

=30.1 x 1021 mlcs

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