# What is the percent composition of water in #"Na"_2"SO"_4 * 10"H"_2"O"#?

##### 1 Answer

Sodium sulfate decahydrate is

#### Explanation:

Your goal here is to figure out how many grams of water you have in

To do that, start with what you know. More specifically, start with the fact that **mole** of sodium sulfate decahydrate contains

,one moleof sodium sulfate#1 xx "Na"_2"SO"_4# ,ten molesof water#10 xx "H"_2"O"#

You also know that sodium sulfate has a **molar mass** of **molar mass** of **mole** of sodium sulfate decahydrate contains

#1 xx "142.04 g " -># sodium sulfate#10 xx "18.015 g " -># water

and has a **total mass** of

#"142.04 g"color(white)(.) + 10 xx "18.105 g" = "322.19 g"#

This means that

#100 color(red)(cancel(color(black)("g Na"_ 2"SO"_ 4))) * (10 xx "18.015 g H" _ 2"O")/(322.19 color(red)(cancel(color(black)("g Na"_ 2"SO"_ 4)))) = "55.9 g H"_2"O"#

Therefore, you can say that the **percent composition** of water in this hydrate is equal to

#color(darkgreen)(ul(color(black)("% H"_2"O" = 55.9%)))#

Keep in mind that the *out of* *of hydrate*.