Multiple choice

In order to determine the volume of blood in an animal without killing it, a 1.00 mL sample of an aqueous solution containing tritium is injected into the animal's blood-stream. The sample injected has an activity of $1.8\times 10^{6}$ cps(counts per second). After sufficient time for the sample to be completely mixed with the animal's blood due to normal blood circulation, 2.00 mL of blood are withdrawn from an animal, and the activity of the blood sample withdrawn is found to be $1.2\times 10^{4}$ cps. Calculate the volume of animal's blood?

  1. $300$ mL
  2. $100$ mL
  3. $200$ mL

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The dilution principle states: C1V1 = C2V2. Total activity = 1.8 * 10^6. Activity per mL in blood = (1.2 * 10^4) / 2 = 6 * 10^3. Total volume = (1.8 * 10^6) / (6 * 10^3) = 300 mL.

AI explanation

By the conservation of activity, the total activity injected into the bloodstream is diluted across the entire volume of the animal's blood. The total activity is 1.8 multiplied by 10 to the power of 6 cps, and the concentration after mixing is measured as 1.2 multiplied by 10 to the power of 4 cps per 2 mL, which is 6000 cps per mL. Dividing the total activity by this concentration gives 1,800,000 divided by 6000, yielding a total blood volume of 300 mL.

Keep practicing — related questions