Finding the Specific Activity of Rubidium Chloride

  • Thread starter Thread starter Phillyfan321
  • Start date Start date
  • Tags Tags
    Activity Specific
Click For Summary

Homework Help Overview

The discussion revolves around calculating the specific activity of natural rubidium chloride, considering the isotopes of rubidium, specifically 85Rb and 87Rb, along with their respective abundances and atomic masses.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss converting grams of RbCl to the number of molecules and applying isotope abundance to find the amount of radioactive 87Rb. There are questions about the necessity of using both atomic masses provided and the implications of the stable isotope on the decay calculations.

Discussion Status

The conversation includes attempts to clarify the concept of specific activity and its relation to the isotopes present. Some participants express uncertainty about their calculations and the relevance of certain values, indicating a need for further exploration of the problem.

Contextual Notes

There is mention of the need to phrase questions with consideration for varying levels of chemistry knowledge among participants. Additionally, some participants express confusion regarding the definitions of terms like Ar and Mr.

Phillyfan321
Messages
3
Reaction score
0

Homework Statement


The element rubidium consists of two isotopes, the stable 85Rb and radioactive 87Rb (abundance 27.83%). What is the specific activity of natural rubidium chloride? Use Ar85.47 gmol-1 for rubidium element, Ar 86.91 gmol-1 for 87Rb, and Mr 120.92 gmol-1 for RbCl.

Homework Equations


A2 = (λ2A1 /λ2-λ1) (e^-λ2 *t)
M = (N#/ avag const)* Ar

The Attempt at a Solution



I tried to convert 1g (subjective choice) of RbCl to 5 x 10^21 molecules, then apply percent abundance to get 1.4 x 10^21 Rb87. I converted that back to grams and got .2. I really don't know if I am on the right track or not, because I can't seem to figure out where I am going with this and if I need the other Ar value. Thanks.
 
Physics news on Phys.org
Phillyfan321 said:

Homework Statement


The element rubidium consists of two isotopes, the stable 85Rb and radioactive 87Rb (abundance 27.83%). What is the specific activity of natural rubidium chloride? Use Ar85.47 gmol-1 for rubidium element, Ar 86.91 gmol-1 for 87Rb, and Mr 120.92 gmol-1 for RbCl.

Homework Equations


A2 = (λ2A1 /λ2-λ1) (e^-λ2 *t)
M = (N#/ avag const)* Ar

The Attempt at a Solution



I tried to convert 1g (subjective choice) of RbCl to 5 x 10^21 molecules, then apply percent abundance to get 1.4 x 10^21 Rb87. I converted that back to grams and got .2. I really don't know if I am on the right track or not, because I can't seem to figure out where I am going with this and if I need the other Ar value. Thanks.
Since this is not a chemistry forum, you will need to phrase your question in a way that assumes little knowledge of chemistry.
 
Well... Specific Activity in this case is Bq per unit mass (Disintegration/sg) which is what I need to find. Only part (28%) of the total compound is radioactive but when I thought of doing a sum for the components the stable isotope doesn't have a decay factor so I ran into a wall.
 
Phillyfan321 said:
Well... Specific Activity in this case is Bq per unit mass (Disintegration/sg) which is what I need to find. Only part (28%) of the total compound is radioactive but when I thought of doing a sum for the components the stable isotope doesn't have a decay factor so I ran into a wall.
Doesn't help me. E.g. what are Ar and Mr?
 

Similar threads

Undergrad Calculation of specific activity when element consists of two isotopes
  • · Replies 1 ·
Replies
1
Views
8K