Question

Calculate the mass of scheelite (CaWO4) that Contains 1 billion (1.00x10^9) Oxygen atoms. Are you sure your answer has a unit symbol if necessary, and rounded to 3 significant digits

Answer 1

The first step to solve this problem is to find how many molecules of scheelite contain 1 billion atoms. To do it, divide 1 billion by 4, this is because each molecule of scheelite contains 4 atoms:

`1.00*10^9atoms\cdot(1molecules)/(4atoms)=2.50*10^8molecules`

Now, use Avogadro's number to find the amount of moles in 2.50x10^8 molecules:

`2.50*10^8molecules\cdot(1mol)/(6.022*10^(23)molecules)=4.15*10^(-16)mol`

Use the molecular weight of scheelite to convert the obtained moles to grams:

`4.15*10^(-16)mol\cdot(287.84g)/(mol)=1.19*10^(-13)g`

The answer is 1.19x10^-13 grams.