# Help with some chemistry please

• 10-29-2003
Zewu
I am studying chemistry, and I am supposed to answer this question, which isn't explained how to solve in its book. I thought you'd might have some experience, so if you do, please explain for me how this is to be solved:

"The relative atomic mass of iridium is 192.2. Iridium occurs naturally as a mixture of iridium-191 and iridium-193. What is the percentage of each isotope in naturally-occuring iridium?"
• 10-29-2003
golfinguy4
x*mass of iridium191 + (1-x)*mass of iridium193=192.2

Solve for x.
• 10-29-2003
Leeman_s
The sum of the percentages of all naturally occuring isotopes equals the atomic mass...thats how they get the atomic mass of elements.
• 10-29-2003
Clyde
Quote:

The sum of the percentages of all naturally occuring isotopes equals the atomic mass...thats how they get the atomic mass of elements
Heh the sum of the percentages equals 100.

But to clarify if i have element Z which has two isotopes, one makes up 20% of all Z and has mass 10, the other makes up 80% of all Z and has mass 20.

The RAM for Z will be 18.

Its basically just the average mass of the element.
• 10-29-2003
Zach L.
Its a weighted average.