You are Here: Home

# How to calculate Isotopic Mass?? HELP PLZ! watch

1. Ok i seriously have no clue how to do this, please explain in the simplest terms thanks

Question: What are the relative abundances of Iridium-191 and Iridium-193 if the R.A.M is 192.2?
2. Bump
3. iridium 191 is x
193 is y

so xs percentage plus ys =100
so x + y =100
and rearranged y = 100 -x

(191 X x / 100) + (193 X 100-x)/100 =192.2
get the 100s off the bottom by multiplying by 100 and then rearrage to find x
and this is x = 40
so y = 60
and they are the abundances
4. (Original post by affleming)
iridium 191 is x
193 is y

so xs percentage plus ys =100
so x + y =100
and rearranged y = 100 -x

(191 X x / 100) + (193 X 100-x)/100 =192.2
get the 100s off the bottom by multiplying by 100 and then rearrage to find x
and this is x = 40
so y = 60
and they are the abundances
Ok thanks dude. Can u check if i did this one is correctly pls:

RAM of Br=79.9 , two isotopes Br-81 and Br-79
i got : Br-81=45% and Br-79=55%

Is that right? thanks
5. Chemistry questions go here: http://www.thestudentroom.co.uk/forumdisplay.php?f=130
6. (Original post by Hanz_a93)
Ok thanks dude. Can u check if i did this one is correctly pls:

RAM of Br=79.9 , two isotopes Br-81 and Br-79
i got : Br-81=45% and Br-79=55%

Is that right? thanks
yep thats right

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: September 28, 2010
The home of Results and Clearing

### 2,536

people online now

### 1,567,000

students helped last year
Today on TSR

### University open days

1. Keele University
Sun, 19 Aug '18
2. University of Melbourne
Sun, 19 Aug '18
3. Sheffield Hallam University