How many moles are 1.20 x 1025 aloms of phosphorous?

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

1 Answer
Feb 23, 2018

#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.)