You are instructed to create 300. mL of a 0.27 M phosphate buffer with a pH of 7

Question

You are instructed to create 300. mL of a 0.27 M phosphate buffer with a pH of 7.2. You have phosphoric acid and the sodium salts NaH_2PO_4, Na_2HPO_4, and Na_3PO_4 available. H_3PO_4(s) + H_2O(I) H_3O^+(aq) + H_2PO_4^-(aq) K_a1 = 6.9 times 10^-3 H_2PO_4^-(aq) + H_2O(I) H_3O^+(aq) + HPO_4^2-(aq) K_a2 = 6.2 times 10^-6 HPO_4^2-(aq) + H_2O(I) + H_2O(I) H_3O^+(aq) + PO_4^3-(aq) K_a3 = 4.8 times 10^_13 Which of the available chemicals will you use for the acid component of your buffer? H_3PO_4 NaH_2PO_4 Na_2HPO_4 Na_3PO_4 Which of the available chemicals will you use for the base component of your buffer? H_3PO_4 NaH_2PO_4 Na_2HPO_4 Na_3PO_4 What is the molarity needed for the acid component of the buffer? M What is the molarity needed for the base component of the buffer? M 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? g How many grams of base are needed for the buffer? g

Explanation / Answer

NaH2PO4 is used as the acid component and Na2HPO4 is used as the base component. Na2HPO4 is the conjugate base of NaH2PO4. Acid is to react with bases added to the system and base is to react with acids.

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