February 25, 2017

Homework Help: Chemistry

Posted by Trixie on Friday, April 16, 2010 at 5:35pm.

One last question...even though no one seems to be willing to help me out without being rude.

The blood volume in a cancer patient was measured by injecting 5.0 mL of Na2SO4(aq) labeled with 35S (t1/2 = 87.4 d). The activity of the sample was 300 µCi. After 22 min, 12.9 mL of blood was withdrawn from the man and the activity of that sample was found to be 0.75 µCi. Report the blood volume of the patient.

I am unsure how the activity fits in here. I know it is equal to the rate of decay=k*N but I am getting really confused with these variables as in the ohter problems. I tried finding k by dividing ln2 by the half life 87.4d (converted to minutes). I then plugged into N'=Ne^-kt, solving for N. my answer just came up to be 12.9mL which clearly is not right....someone please help me with at least one o these problems....I am trying to learn it and cannot get a hold of my professor. I guess that's what happens when the student ratio is 240:1.

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