please answer based on the chart provided. Thanks 5.0 Electrolyte Preparation Th

Question

please answer based on the chart provided. Thanks

5.0 Electrolyte Preparation The chemical make-up and composition of model-ISF is as follows: 1 L MVV mTMII ionic component grams in HPO. 7H20 0.536 268.07 2 0.069 138.00 os NaH2PO4 H20 NaHCO, 2.352 84,01 28 Co, 0.751 100.12 75 6428 58.44 110 NaCI 0,060 120.39 MgSO4 0,048 95.22 MgCl 110.99 0,5 CaCl2 Model ISF is prepared in a 1 Lvolume according the following procedure: In a 50 ml Erlenmeyer flask add 0.056 g of Cach and 25 ml of deionized water 15 Ms2 for all

Explanation / Answer

1) Given that

     [NaH2PO4] = 0.5 mM

    [Na2HPO4] = 2 mM

We know that pKa of NaH2PO4 = 7.2

From Henderson-hasselbalch equation,

pH = pKa + log [conjugate base] /[acid]

     = pKa + log [Na2HPO4] /[NaH2PO4 ]

     = 7.2 + log ( 2 mM/ 0.5 mM)

   = 7.8

pH = 7.8

Therefore,

pH of the buffer = 7.8

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