# Question #74a4c

##### 1 Answer

#### Explanation:

Your starting point here will be to determine how many grams of zinc are present in

You know that zinc sulfide has a **molar mass** of **mole** of zinc sulfide has a mass of

Elemental zinc, **molar mass** of **mole** of zinc has a mass of

Now, the chemical formula of zinc sulfide tells you that **mole** of zinc sulfide contains **mole** of zinc, so you can use the molar masses to say that **mole** of zinc sulfide, contains **mole** of zinc.

This means that

#5.00 color(red)(cancel(color(black)("g ZnS"))) * "65.38 g Zn"/(97.474 color(red)(cancel(color(black)("g ZnS")))) = "3.354 g Zn"#

So, you know that your *crude sample* contains **total mass** of **percent composition** of zinc in the crude sample, simply divide the mass of zinc by the **total mass** of the sample and multiply the result by

#(3.354 color(red)(cancel(color(black)("g"))))/(8.00color(red)(cancel(color(black)("g")))) * 100% = color(darkgreen)(ul(color(black)(41.9%)))#

The answer is rounded to three **sig figs**.

Notice that the **percent composition** of zinc in zinc sulfide

#(3.354 color(red)(cancel(color(black)("g"))))/(5.00color(red)(cancel(color(black)("g")))) * 100% = 67.1%#

if **higher** than the percent composition of zinc in the crude sample because you're dealing with the same mass of zinc in a smaller mass, i.e. in