How do you find formula mass?

1 Answer
anor277
Jun 28, 2016

Got a Periodic Table handy?

Explanation:

Consider the formula, and sum up the masses of each element in the formula to give the formula mass. You get an answer in #g*mol^-1, "a mass in gram per Avogadro's number of atoms"#.

So let's take an example: #OsO_4# (I don't know why I chose that one!). In #1# #mol# of this stuff, there are #1# #mol# metal atoms, and #4# #mol# of #O# atoms. I take the masses from the Periodic Table, and I get a mass of #{190.23(Os)+4xx15.999(O)}*g*mol^-1=254.23 *g*mol^-1#.

You can of course do this with any given formula. You will have access to a Periodic Table in any Chemistry or Physics examination.

Related questions
See all questions in Atomic Mass
Impact of this question
1683 views around the world
You can reuse this answer
Creative Commons License