# Question #93a29

##### 1 Answer

#### Explanation:

In order to go from *grams* of potassium sulfide, *moles* of potassium sulfide you must use a **conversion factor**.

This conversion factor is given by the **molar mass** of the compound. As you know, the **molar mass** of a compound tells you the mass of exactly **mole** of said compound.

In your case, potassium sulfide has a molar mass of

#"every mole of K"_2"S" stackrel(color(white)(color(red)("has a mass of")aaa))(->) "110.26 g"#

You want to go from grams to moles, so set up the molar mass as

#("1 mole K"_2"S")/"110.26 g"#

Now all you have to do is to multiply the number of grams of potassium sulfide by this conversion factor

#12.6 color(red)(cancel(color(black)("g"))) * ("1 mole K"_2"S")/(110.26color(red)(cancel(color(black)("g")))) = color(darkgreen)(ul(color(black)("0.114 moles K"_2"S")))#

The answer is rounded to three **sig figs**, the number of sig figs you have for the mass of potassium sulfide.