posted by .

Naturally occurring cobalt consists of only one isotope, cobalt59, whose relative atomic mass is 58.9332. A synthetic radioactive isotope of cobalt60, relative atomic mass 59.9338, is used in radiation therapy for cancer. A 1.8155 sample of cobalt has an apparent "atomic mass" of 58.9901.

FIND THE MASS OF COBALT60 IN THIS SAMPLE.

I DON'T KNOW WHERE TO START, I TRIED DOING CONVERSION FACTORS BUT I CANT GET A REASONABLE MASS.

HELP?

Let x = fractional abundance Co60
1-x = fractional abundance Co59
(Note that as percentages that will be x% and 100%-x%). Then
x(atomic mass Co60) + (1-x)(atomic mass Co59) = 58.8901
Solve for x and 1-x will give you the fractinal abundances of Co59 and Co60. Then fraction * 1.8155g = grams Co60 or Co59 depending upon which fraction you use. Post your work if you get stuck.

I get....
(x)(59.9338) +(1-x)(58.9332) =(58.9901)
59.9338x+58.9332-58.9332x=58.9901
1.0006x=0.0560
x=0.0569

cobalt60 abundance=0.0569%
cobalt59 abundance=0.9431%

0.0569/0.9431 X 1.8155g = .10953grams
Is that right?? It looks like i did it wrong.

We get...
OH wait, do we do

0.0569 X 1.8155g = 0.103g ?

so cobalt60=0.103g

Thanks!

Everything looks ok except where you converted to percent (which the problem didn't ask for). x = 0.0560 = Co60 abundance which is 5.60% if yu want to convert to percent.

## Similar Questions

1. ### Chem

Naturally occurring cobalt consists of only one isotope, cobalt59, whose relative atomic mass is 58.9332. A synthetic radioactive isotope of cobalt60, relative atomic mass 59.9338, is used in radiation therapy for cancer. A 1.8155 …
2. ### chemistry

Copper has two naturally occurring isotopes. Cu-63 has a mass of 62.939 amu and relative abundance of 69.17%. Use the atomic weight of copper to determine the mass of the other copper isotope.
3. ### chemistry

Naturally occurring cobalt consists of only one isotope Co59 whose relative atomic mass is 58.9332. A synthetic radioactive isotope of cobalt Co60, relative atomic mass 59.9338, is used in radiation therapy for cancer. A 1.8516 sample …
4. ### Chemistry

Naturally occurring boron is 80.20% boron-11 (of atomic mass 11.01 amu) and 19.80% of some other isotope form of boron. What must be the atomic mass of this second isotope in order to account for the 10.81 amu average atomic mass of …
5. ### Chemistry

Silver has an average atomic mass of 107.9 u and is known to have only two naturally occurring isotopes. If 51.84% of Ag exists as Ag-107 (106.9051 u), what is the identity and the atomic mass of the other isotope?
6. ### chemistry

Calculate the atomic mass of naturally occurring molybdenum (Mo) which contains the following isotopes. Isotope Abundance (%) Atomic mass (a.u.) 92Mo 15.8 91.91 94Mo 9.0 93.90 95Mo 15.7 94.91 96Mo 16.5 95.91 97Mo 9.5 96.91 98Mo 23.5 …
7. ### Chemistry

Naturally occurring cobalt consists of only one isotope, 59Co, whose relative atomic mass is 58.9332. A synthetic radioactive isotope of cobalt, 60Co, relative atomic mass 59.9338, is used in radiation therapy for cancer. A 1.8276g …
8. ### Chemistry

1. A hypothetical pure element consists entirely of two isotopes. The natural percent abundance of the isotope with mass 25.5 u is 86.1%. The other isotope has mass 29.2 u. Calculate the atomic weight of the naturally occurring element. …
9. ### Chemistry

1)Naturally occuring boron is made up of 20% by mass of 10B isotope and 80% by mass of 11B isotope.Calculate the relative atomic mass of boron. (2)Natural Silicon containing ores contains 92% of 28Si, 5% of 29Si and 3% of 30Si.Calculate …
10. ### Chemistry

A hypothetical pure element consists entirely of two isotopes. The natural percent abundance of the isotope with mass 25.5 u is 78.8 percent. The other isotope has mass 29.5 u. Calculate the atomic weight of the naturally occurring …

More Similar Questions

Post a New Question