Question

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Calculate how many milliliters of 0.622 M KOH should be added to 4.90 g of MOPS (see the Structures and pKa Values for Common Buffers table) to give a pH of 7.77. 4.0 23.3 XmL

Answer 1

1 mol No of moles of MOPS, HX =0.0219 mol 4.90 g x- 223.3 g pH of the buffer = 7.77 pK of weak acid MOPS, pK 7.18 ICE table X HO OH НХ I(mol) C(mol): Е(mol). 0.0219 0 x 0.0219 x 0 According to Hen derson equation РН %3DpК, + 10g HX 7.77 7.18 log 0.0219 x log 0.0219 = 0.59 = 100.59 = 3.89 0,0219 x x 0.0174 mol According to the ICE table, no of moles of base added =xmol = 0.0174 m ol 1 L 1000 mL X Volume of KOH added 0.0174 mol x 0.622 mol 1 L = 27.97 mL 28.0 mL