General Chemistry Donald McQuarrie Peter A. Rock Ethan Gallogly University Scien
ID: 948504 • Letter: G
Question
General Chemistry Donald McQuarrie Peter A. Rock Ethan Gallogly University Science Books presented by Sapling Learning 4th Edition Map Phosphorous acid, H3PO3(aq), is a diprotic oxyacid that is pKa1PKa2 an important compound in industry and agriculture 1.30 6.70 Calculate the pH for each of the following points in the titration of 50.0 mL of a 2.1 M H3PO3(aq) with 2.1 M KOH(aq) Number Phosphorous acid (a) before addition of any KOH Number (b) after addition of 25.0 mL of KOH Number (c) after addition of 50.0 mL of KOH Number (d) after addition of 75.0 mL of KOH Number (e) after addition of 100.0 mL of KOHIExplanation / Answer
a) Ph = -log [H+]
= -log [ 2.1] = 0.3322
b ) Vol of H3PO3 = 50 ml
Vol of KOH = 25 ml
Unreacted H3PO3 = 50 - 25 = 25 ml of 2.1 M
Total volume = 50 + 25 = 75 ml
Conc of H3PO3 = 2.1 / 75 = 2.8 x 10-2
pH = -log [H+]
= -log [ 2.8 x 10-2]
= 1.55
c )
Vol of H3PO3 = 50 ml
Vol of KOH = 50 ml
Unreacted H3PO3 = 50 - 50 = 00 ml of 2.1 M
Total volume = 50 + 50 = 100 ml
Conc of H3PO3 = 2.1 / 100 = 2.1 x 10-2
pH = -log [H+]
= -log [ 2.1 x 10-2]
= 1.67
d)
Vol of H3PO3 = 50 ml
Vol of KOH = 75 ml
Total volume = 50 + 75 = 125 ml
Conc of H3PO3 = 2.1 / 125 = 1.65 x 10-2
pH = -log [H+]
= -log [ 1.68 x 10-2]
= 1.77
e )
Vol of H3PO3 = 50 ml
Vol of KOH = 100 ml
Total volume = 50 + 100 = 150 ml
Conc of H3PO3 = 2.1 / 150 = 1.4 x 10-2
pH = -log [H+]
= -log [ 1.4 x 10-2]
= 1.85
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