here is a question says : enter image description here

I know that atom's number is found by = $6.022*10^{23} * mol$

but how this formula is used here is what i dont know

what's the $idea$ of this question?


You need more information. They probably expect you to look in a book and see that the atomic weight (which is a weighted average over all isotopes) of $\ce{Tl}$ is 204.383. Now if x is the amount of $\ce{^203Tl}$ with atomic weight 202.97 and (1-x) is....

Does that get you started?

$$\ce{(x*202_{.}97) + ((1-x)*204_{.}97)~=~?}$$

Can you get to the answer from here?

| improve this answer | |
  • $\begingroup$ could you write one more line? $\endgroup$ – Maher Jun 20 '14 at 0:57
  • $\begingroup$ I think i got it. The final answer is 2.51, right? $\endgroup$ – Maher Jun 20 '14 at 20:38
  • $\begingroup$ Set the above equation equal to 204.383 and solve for x, the fractional amount of the TL 203 isotope. You'll find that x=29%. So about 29% of the 203 isotope and (1-.29) or 71% of the 205 isotope. $\endgroup$ – ron Jun 20 '14 at 21:38

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.