Concentration problem using absorbance

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SUMMARY

The discussion centers on calculating the mass of phosphorus eliminated by a patient based on urine analysis using absorbance measurements. A 1.00-mL aliquot of urine was diluted to 50.00 mL and analyzed at 650 nm, revealing a phosphate concentration of 2.5 ppm. The confusion arises from the distinction between phosphorus and phosphate, as the method measures phosphate concentration while the questions refer to phosphorus. The relationship between the two is clarified, emphasizing that each phosphate molecule contains one phosphorus atom.

PREREQUISITES
  • Understanding of absorbance and spectrophotometry
  • Knowledge of the Beer-Lambert Law (A = abC)
  • Familiarity with phosphate and phosphorus chemistry
  • Basic skills in unit conversion (ppm to mmol/L)
NEXT STEPS
  • Research the Beer-Lambert Law applications in analytical chemistry
  • Learn how to convert concentrations from ppm to mmol/L
  • Study the chemical properties and differences between phosphorus and phosphate
  • Explore methods for preparing calibration curves in spectrophotometric analysis
USEFUL FOR

This discussion is beneficial for chemistry students, laboratory technicians, and anyone involved in analytical chemistry, particularly those working with spectrophotometric methods for analyzing biological samples.

Rujano
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Homework Statement



Hi. A patient produced 1122 mL of urine in 24 hours.
A 1.00-mL aliquot of the sample was treated with
Mo(Vl) and ascorbic acid and was diluted to a
volume of 50.00 mL. A calibration curve was pre-
pared by treating 1.00-mL aliquots of phosphate
standard solutions in the same manner as the urine
sample. The absorbances of the standards and the
urine sample were obtained at 650 nm, and then
concentration of 1.00ml diluted aliquots of phosphate is found 2.5ppm.

What mass in grams of phosphorus was eliminated per day by the patient?

What is the concentration of phosphate in the urine (mmol/L)?

Homework Equations



A = abC

The Attempt at a Solution



Ok, what I really don't get is why in the first question they ask me for PHOSPHOROUS and in the second one for PHOSPHATE. And again, in the problem it says that this is a method used to determine PHOSPHOROUS, yet the standards are made of PHOSPHATE.

It's really confusing to me... they shouldn't be the same thing, right?
 
Physics news on Phys.org
Phosphate contains phosphorus - one atom per molecule.
 

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