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You are instructed to create 400. mL of a 0.39 M phosphate buffer with a pH...

You are instructed to create 400. mL of a 0.39 M phosphate buffer with a pH of 6.2. You have phosphoric acid and the sodium s

You are instructed to create 400. mL of a 0.39 M phosphate buffer with a pH of 6.2. You have phosphoric acid and the sodium salts NaH2PO4, Na2HPO4, and Na3PO4 available. (Enter all numerical answers to three significant figures.) H3PO4(s) + H20(I) =H30+ (aq) + H2PO4 (aq) Kai = 6.9x10-3 H2PO4 (aq) + H20(1) =H30+ (aq) + HPO42-(aq) Ka2 = 6.2 x 10-8 HPO42-(aq) + H20(1) = H30+(aq) + PO43-(aq) Ka3 = 4.8x10-13 Which of the available chemicals will you use for the acid component of your buffer? ОН3РО4 NaH2PO4 Na2HPO4 Na3PO4 Which of the available chemicals will you use for the base component of your buffer? OH3PO4 NaH2PO4 Na2HPO4 Na3PO4 What is the molarity needed for the acid component of the buffer? What is the molarity needed for the base component of the buffer? How many moles of acid are needed for the buffer? mol How many moles of base are needed for the buffer? mol How many grams of acid are needed for the buffer?
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Answer #1

Question 1. NaH2PO4

Explanation: pH is close to pKa2

Question 2. Na2HPO4

Explanation: pH is close to pKa2

Note: pKa2 = -Log(Ka2) = -Log(6.2*10-8) = 7.2

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