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To make 1.00 L of a 0.100 M H2PO4- / HPO42- buffer at pH 6.90 and...

To make 1.00 L of a 0.100 M H2PO4- / HPO42- buffer at pH 6.90 and you start with the NaH2PO4,

A. Calculate the mass of NaH2PO4 needed to make the buffer.

B. Should HCl or NaOH be added to make the final buffer? Calculate the number of moles of HCl or NaOH that needs to be added.   Note: formula mass of NaH2PO4 is 120.

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Answer #1

Total moles of H2PO and HPO is the initi al moles of NaH,PO, mol NaH2PO4 = 1.00 L × 0.100 M = 0.100 mol Mass of NaH2PO, - mol

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