1. What is the weight percent of phosphorus in anhydrous potassium dihydrogen ph

Question

1. What is the weight percent of phosphorus in anhydrous potassium dihydrogen phosphate?

2. 0.1075 g of anhydrous potassium dihydrogenphosphate are used to prepare 500 mL of the 50 mg/L (approximate) stock solution of P. The instructions guide you to make a subsequent STANDARD P solution. Following the procedure described in the lab manual, what is the volume you must use of STANDARD P solution to make a 100 ?g/L P standard? (Express your answer with 4 sig figs)

I would like to know how to solve these two problem! Thanks

Explanation / Answer

KH2PO4
Total weight = 136.086 g/mol
Phosphorus weight = 31
31 / 136 = 0.2279 = 22.8%

2) 50 mg/L = 107.5 mgof KH2PO4 / unknown volume
    unknown volume = 107.5 / 50 = 2.15 L
MV=M2V2
(50 mg/L)(2.15 L)= (100 mg/L) ( V2)
V2=1.075 L

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