How many molecules are in a sample of water with a mass of 44.99 grams?

1 Answer
anor277
Mar 5, 2016

#"Mass "rarr" Moles "rarr" Number of molecules"#

Explanation:

To get the number of moles, we divide the mass by the molar mass:

#(44.99*g)/(18.01*g*mol^-1)# #=# #2.50*mol#.

Now by definition, in a mole of stuff there are #6.022xx10^23# individual items of that stuff.

So, in the given quantity of water, there are #6.022xx10^23*mol^-1xx2.50*mol# #=# #15.04xx10^23" water molecules"#.

How many oxygen atoms in such a quantity; how many hydrogen atoms?

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