How are percent mass calculations used?
a.
they are used for determining concentrations in solutions and water of hydration
c.
they are used for determining water of hydration and the combustion analysis of hydrocarbons
b.
they are used for determining molecular purity and concentration in solutions
d.
none of the above

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

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~ trueboss72