How many moles of "H"_2"O" contain 2.60 * 10^23 molecules of water?

The answer is 0.432 mole of H2O but I dont know how to get that answer. I dont know how to set up the problem

2 Answers
Sydney ยท Stefan V.
Jul 10, 2018

0.432mol

Explanation:

Divide the given number of molecules by Avogadro's constant. Avogradro's constant is the number of atoms/molecules in a mole of a substance.

Therefore,

(2.60 * 10^23 \ "molecules")/(6.022 * 10^23 \ "molecules/mol") = "0.432175 moles" ~~ "0.432 moles"

anor277
Jul 10, 2018

Well, how molecules are present in ONE MOLE of water...?

Explanation:

By definition, there are 6.022xx10^23 such molecules, or N_A such molecules in ONE mole of water. And thus in such a quantity there are N_A oxygen atoms, and 2xxN_A hydrogen atoms...and the mass associated with this numerical quantity of water molecules is approx. 18*g...

And so we simply take the quotient....

"Moles of water"=(2.60xx10^23*"water molecules")/(6.022xx10^23*"water molecules"*mol^-1)

=0.432*mol...and thus a mass of 0.432*molxx18.01*g*mol^-1=7.78*g...

Instead of the mole, we could use the dozen, or the gross, or some other numerical quantity ... it just happens that one mole of hydrogen ATOMS have a mass of 1*g more or less precisely.. which is why we use this absurdly large quantity .. Capisce?

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