Chem

Okay so I have this assignment and I thought I knew how to do this but appearntly I am just lost. I know what the answer is suposed to be and I am deifantly no wheres near that. If you can sorta point me in the right direction that would be great. Thanks! The question is:

The isotope 99mTc, (t ½ = 6.01 hours) is used in the diagnostic imaging of the heart and other organs. For diagnosing heart function, a particular dose has an activity of 3.09 x 108 disintegrations per second. Calculate the mass in grams of 99mTc required to produce this activity level. Use 98.91 amu as the atomic mass of 99mTc.

I thought you would use A=landaN and solve for N. And then you woudl get landa by using landa=0.693/(t1/2) and then just divide the amount for N by avagadros number to get moles, then change the moles to grams. Then chnage the mass they give you to grams and multiply the moles that you found for N by the gram amount and you would get the mass. I don't know if that makes sense but it does on my paper.


Use Activity= lambda*N Yes, lambda is .693/t1/2. Yes, you proceeded correctly, get moles, then grams.

N/avonumber * 98.91 = mass you are looking for.


But that doesnt work out cause that's what I did. But you still need to chnage to grams, and when you do it is WAYYYY wrong. lol I'm so confused


let me see your calcs.


Okay:
A= 3.09 X10^8 dis./s
t1/2= 6.01hrs

A=landaN
N=A/landa
Units are in seconds so gotta chnage the t1/2 to seconds
Landa=(0.693/6.01hrs)(1hr/60min)(1min/60s)
=0.00003203 /s

N=(3.09 x 10^8 dis/s)/(0.00003203 /s)
= 9.647205745 x 10^12 N

9.647205745 x 10^12N(1mol/6.022 x 10^23)
= 1.601993647 x 10^-11mol

98.91amu(1.66054 x 10^-24g /1amu)
= 1.642440114 x 10^-22g

= 1.601993647 x 10^-11mol (1.642440114 x 10^-22g /1mol)
=2.63 x 10^-33g

The answer is supposed to be 1.58 x10^-9g


Okay:
A= 3.09 X10^8 dis./s
t1/2= 6.01hrs

A=landaN
N=A/landa
Units are in seconds so gotta chnage the t1/2 to seconds
Landa=(0.693/6.01hrs)(1hr/60min)(1min/60s)
=0.00003203 /s

N=(3.09 x 10^8 dis/s)/(0.00003203 /s)
= 9.647205745 x 10^12 N

9.647205745 x 10^12N(1mol/6.022 x 10^23)
= 1.601993647 x 10^-11mol
<font=14>You are OK to here. Now just multiply 1.602 x 10^-11 x 98.91 = 1,58 x 10^-9 g</font=12>
98.91amu(1.66054 x 10^-24g /1amu)
= 1.642440114 x 10^-22g

= 1.601993647 x 10^-11mol (1.642440114 x 10^-22g /1mol)
=2.63 x 10^-33g

The answer is supposed to be 1.58 x10^-9g



N/avonumber * 98.91 = mass you are looking for.

But N= A/lambda= A*t1/2/.693

Now t1/2 has to be in seconds...

N= 3.09E8*6.01hr*3600sec/hr /.693
N= 9.65E12

mass= N/avonumber * 98.91
=9.65E12*98.91/6.02E23
=1.59 nanograms

check that.


Ohhh okay. so I think what I was doing wrong was just the fact that I was changing the AMU to grams, then dividing it and I forgot that amu can be considered grams at some points/


Okay thanks, I think I got it. I got 2.0E-9 so at least I know I'm in the right area. Thanks sooooo much.


I went through this independently and obtained 1.58 x 10^-9 g, also.

  1. 👍 0
  2. 👎 0
  3. 👁 126

Respond to this Question

First Name

Your Response

Similar Questions

  1. science (any tutor)

    2. How did Darwin and Lamarck differ in their thinking about change in species? A.Darwin thought that organisms could induce their own changes, while Lamarck thought that change could only be induced by an organism’s

  2. statistics

    What are the chances that a person who is murdered actually knew the murderer? About 64% of people who are murdered actually knew the murderer. Suppose that a detective file in New Orleans has 63 unsolved murders. What is the

  3. spanish

    Give the correct form of the appropriate verb, saber or conocer, which would be used in writing the fol- lowing sentences in Spanish. 12. _______ Maria knew everyone. 13. _______ Because he had already seen the movie, he knew what

  4. Language Arts

    Which revision to sentence 3 contains an example of vivid description? 1) Tess turned and faced the podium. 2) She knew that once she walked up to the microphone, she would have to make a statement. 3) She thought a moment. A. She

  1. History

    George Washington was an enormously popular general. Why didn't he try to become a king? He believed in a republican form of government. He knew the army would be hard to control. He thought future monarchs would abuse power. He

  2. U.S. History

    George Washington was an enormously popular general. Why didn't he try to become a king? He believed in a republican form of government.*** He knew the army would be hard to control. He thought future monarchs would abuse power.

  3. Spanish

    Give the correct form of the appropriate verb, saber or conocer, which would be used in writing the following sentences in Spanish. 12. C Maria knew everyone. 13. S Because he had already seen the movie, he knew what happened? 14.

  4. English 1

    my assignment "suppose the person to whom Montresor is telling his sstory has turned him over to the police. Montresors lawyer might argue that his client is insane. the prosecution will argue that montresor knew exactly what he

  1. English 10th Grade

    Choose the answer that shows a correct revision to the following sentence: Why if you did not want to hear it did you ask me what I thought a) Why, if you did not want to hear it, did you ask me what I thought? b) Why, if you did

  2. English

    ) (4) Her carpets were planned for, so not woven, until she knew the size of the room in her new home in which it was to be used. Read the passage. Look at the underlined section marked number 4. There may be a mistake in the way

  3. Math

    Mara finished 1/5 of her assignment on Saturday and 3/8 of her assignment on Sunday. What fraction of her assignment did she complete on Saturday and Sunday? --Thank you!--

  4. Art

    I just did an assignment for art, and now it wants me to do this "Critique worksheet" thing. One of the parts on it is "Overview of assignment" What am I supposed to put there?

You can view more similar questions or ask a new question.