How many moles are in 349.3 g of H2O

19.38 moles

Explanation: When in doubt, use stoichiometry

Molar mass of H2O = 2(molar mass H) + molar mass O

=2(1.01) + 16.00 = 18.02

Now, you just convert:

349.3g(1 mol H2O/18.02gH2O)

= 19.384

But the value given has 4 significant figures, so we write it as 19.38

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