Question

How many moles are 1.20 x 1025 aloms of phosphorous?

can you show the work and explaining how you got the answer.

Answer 1

`19.969` moles or `20.0` moles using significant figures

Explanation:

A mole is a unit of measurement, but more specifically, it is an amount. Just like a dozen of a thing means 12 things, a mole measures the amount of something. The number of a certain thing in a mole is `6.022*10^23`; that number is called Avogadro's number. So a mole of potatoes is `6.022*10^23` potatoes, or a mole of cars is `6.022*10^23` cars.

This can be applied to chemistry to help convert between atoms to grams. The beauty of Avogadro's number is that `6.022*10^23` molecules of a certain compound weighs its atomic mass in grams. For example, iron trichloride `FeCl_3` has an atomic mass of 162.195. So a mole of `FeCl_3` weighs 162.195 grams.

Now that the concept of moles is established, you know that a mole of anything has `6.022*10^23` things in it. For phosphorous or any chemical compound, a mole contains `6.022*10^23` molecules in it. So if you have `1.20* 10^25` (that's what I assume you meant) atoms of phosphorous, then just divide by Avogadro's number to find the number of moles.

`(1.20* 10^25 ATOMS)/ (6.022*10^23 (ATOMS)/(MOL)`

You would get `19.969` moles. (Notice how when you simplify the units, you will end up with just moles which is the right unit.)