Question

How do you calculate the percent composition of water?

Answer 1

Explanation:

For water we have to calculate it % of Oxygen and % of Hydrogen

Its long calculation to do it here but this video will help

Answer 2

Since water is `"H"_2"O"` (molar mass is `"18.015 g/mol"`), it implies we have a percent composition of `"H"` and one for `"O"`.

Given that chemical formula, we have two equivalents of `"H"`, for which we can use its molar mass, `M_"H" = "1.0079 g/mol"`. We also have one equivalent of `"O"`, for which we can use its molar mass, `M_"O" = "15.999 g/mol"`.

The percent composition (by mass) of `"H"` is written in terms of a unified ratio of the molar masses is

`%"H" = (2xxM_"H")/(M_("H"_2"O"))xx100%`

`= (2xx"1.0079 g/mol")/("18.015 g/mol")xx100%`

`~~ color(blue)(11.19% "H")`

Similarly for `"O"`, we have

`%"O" = (1xxM_"O")/(M_("H"_2"O"))xx100%`

`= ("15.999 g/mol")/("18.015 g/mol")xx100%`

`~~ color(blue)(88.81% "O")`

Thus, the percent composition of water, by mass, is `11.19%` hydrogen and `88.81%` oxygen.