2 One of the common methods used to determine phosphorus in urine isto treat urine with molybdenum(VI) resulting in a complex compoundof 12- molybdophosphate and then reduced using ascorbic acid produces a blue-colored compound called molybdenum blue (max = 650 nm). A patient's urine sample collected over 24 hours produced 1122 ml. of urine. A total of 1 mL of the sample was treated with Mo(VI) and ascorbic acid and diluted until it reached a volume of 50 mL. A calibration curve is also prepared by treating 1 mL of standard phosphate solution in the same way. The absorbance of the standard solution and the sample was then measured at a wavelength of 650 nm and produced the following data: Solution Absorbance at λ 650 nm Phosphate 1 ppm Phosphate 2 ppm Phosphate 3 ppm Phosphate 4 ppm Urine sample 0,230 0,436 0,638 0,848 0,518 a. Create a calibration curve for the data and determine the slope, intercept, and R values of 2! Determine the concentration of phosphates found in urine samples in units of ppm and mM! b. Determine the mass of phosphate excreted by the patient for 24 hours?

Water contains 500 mg/L of calcium as Ca?*. It is desired to remove the calcium via precipitation to form calcium hydroxide Ca(OH)2. The solubility product Ksp for calcium hydroxide is 8x106. Report the percentage of calcium able to be removed at pH values of 7,8, 9, 10 and 11. Determine the pH required for 90% removal via precipitation. If this process is to be conducted in a full rectangular contact basin 2m deep x 2m wide x 4 m long, calculate and compare the mass of solid precipitate produced at each pH examined above.

The quenching of tryptophan fluorescence by dissolved O₂ gas was monitored by measuring the emission lifetimes at 348 nm in aqueous solutions. [0₂]/(10-² mol dm¯³) 0 T/(10-⁹ s) From the data above, predict the value of [O₂] required to decrease the intensity of tryptophan emission to 50% of the unquenched value. O 3.0 E-2 M O 0.95 E-2 M O None of the choices O 4.3 E-2 M O 1.8 E-2 M 2.6 2.3 5.5 8 10.8 1.5 0.92 0.71 0.57