Mole/Examples/Water

From ProofWiki
Jump to navigation Jump to search

Example of Mole

$1$ mole of water has a mass of (approximately) $18$ grams.


Proof

By definition, a molecule of water is composed of:

$2$ atoms of hydrogen
$1$ atom of oxygen.

It follows that $1$ mole of water is composed of:

$2$ moles of hydrogen
$1$ mole of oxygen.


The (by far) most plentiful isotopes of these elements are:

hydrogen-$1$, with an atomic mass of approximately $1$
oxygen-$16$, with an atomic mass of approximately $16$.


From Mass of Mole of Isotope of Element:

the mass of $1$ mole of hydrogen-$1$ is $1 \ \mathrm g$
the mass of $1$ mole of oxygen-$16$ is $16 \ \mathrm g$.


Hence the mass of $1$ mole of water is $2 \times 1 + 16 = 18$.

$\blacksquare$


Sources