## ilovebmth1234 one year ago Thallium consists of about 30% Th-203 and 71% Th-205. The relative mass will be closest to what value? Question 5 options: A) 201 B) 202 C) 203 D) 204

1. ilovebmth1234

@BioHazard9064 @arronq

2. aaronq

This involves some simple math. The molar mass of an element (as listed on the periodic table) accounts for all the isotopes of that element in a weighted average according to their abundance in nature. $$\sf Molar~mass=\sum(abundance~~\%*m_{isotope~i})$$ $$\sf Molar ~mass_{Th}=0.3*m_{Th-203} + 0.71*m_{Th-205}$$

3. ilovebmth1234

ummm okay

4. aaronq

So all you do is multiply the abundance of each isotope by it's respective mass then add these values together.

5. aaronq

The mass is indicated after the dash. For example, the mass of Th-203 is 203 lol

6. ilovebmth1234

so D?

7. aaronq

sounds right

8. ilovebmth1234

thanks

9. aaronq

no probs

10. ilovebmth1234

i got a couple more questions are you busy?

11. aaronq

nope, post them

12. ilovebmth1234

okay thank you