Question

Questions 13–15 concern the following analysis: A serum sample is analyzed for potassium by flame emission spectrometry using the method of standard additions. Two 0.500-mL aliquots of serum are added to 5.00-ml portions of water. To one portion is added 20.0 uL of 0.0750 M KCI solution. The net emission signals in arbitrary units are 23.2 and 68.6? 13. What is the magnitude of the emission signal produced by the standard? Final answer: 14. How many millimoles potassium are present in the serum? Final answer: 15. What is the concentration of potassium in the serum? Final answer:

Answer 1

20AL 0.02mL inal concentration of kee in sution 9 1 0.060 27 M 0.02 m L X 0-075M= 5.52MLX1 5.00t 0.5 mL +0.0 2) = 5.52mL=total volume (68.6-23 2) = 45.4 units Intenity dueto standand 3 as the mtensity is due to both benun amd stamdary (intensityo covcnt ation) IA 232 2 3.2 68.6z = 40.00626 2 3.2x G8.6 0-00027+x 45 42 0-006 26 38 X M Kcl coneambation = 1.38XM .4 = .3 8X10 m mol m L (5 00+0 5 5.5mL ibthe total v olume mi92i moles of Potassium 4 in solution- 38 Xiox 55 4 6.5 X1 38X10 '= 0-5Xx 4 = .6Xlmmot mof in serum (15.2x10x KO-5 mmol =15.2X10 mmog m L 7-6Xlo mmol 15 ktS. 2X M 0