# Chemistry

posted by on .

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 After 22 min, 12.9 mL of blood was withdrawn from the man and the activity of that sample was found to be 0.75 µCi.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.

• Chemistry - ,

DrBob222 had good advice to you. He was not being rude. Go go bed and get a good night's sleep. These problems will look easier then.

Yes, a student/teacher ratio of 240:1 is an impossible situation -- both for the students and the instructor.

• Chemistry - ,

I wasn't talking about DrBob being rude...that would be bobpursely...DrBob has been nothing but helpful while I have used this site as a resource.

• Chemistry - ,

I also posted the above well before Dr. Bob had answered one of my other questions...