You would like to make a buffer that has a pH of 7.00. Starting with 100.0...

You would like to make a buffer that has a pH of 7.00. Starting with 100.0 mL solution of 0.10 M NaH₂PO₄ and 0.10 M Na₂HPO₄, how much 0.1 M NaOH would you need to add to bring the pH of the buffer up to 7.00?

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Expert Solution

pH = 7.00

pKa = 7.21

millimoles of NaH2PO4 = 100 x 0.1 = 10

H2PO4- + NaOH -----------> HPO42-

10 0.1V 0

10 - 0.1V 0 0.1V

pH = pKa + log [salt / acid]

7.00 = 7.21 + log [0.1 V / 10 - 0.1 V]

[0.1 V / 10 - 0.1 V] = 0.6166

0.1 V = 6.166 - 0.06166 V

V = 38.14

volume of NaOH = 38.14 mL

queen_honey_blossom answered 1 year ago

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