Reaction Between a Polyprotic Weak Acid and a StrongBaseThe reaction of a weak polyprotic acid and a strong base is alittle more complicated but is nonetheless similar to what wehave done.Example:What is thefnal pH of a reaction between 25 mlof a 0.10 M Vitamin C (H2C6H6O6) solution and 25 mL ofa 0.20 M NaOH solution? TheKa1=7.9×10−5andKa2=1.6×10−12.Like above we write a balanced reactionH2C6H6O6+2NaOHNa2C6H6O6H2OH2C6H6O6OH−C6H6O2−6H2OAll the NaOH reacted with the vitamin C to produce onlyC6H6O2−6.The concentration of C6H6O2−6is0.025LH2C6H6O6×0.10mol H2C6H6O6L×0.10mol C6H6O2−60.10mol H2C6H6O6=0.0025mol C6H6O2−6The total volume after the reaction is 50 mL so,£C6H6O2−6¤=0.0025mol C6H6
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This document was uploaded on 11/01/2011 for the course CHM 2046 at University of Florida.