1 This document contains extra practice problems involving equilibrium, acid/base, buffer, and titration calculations. The exam will also include short answer conceptual questions on these topics. 1.A 0.0560 g quantity of CH3COOH is dissolved in enough water to make 50.0 mL of solution. Calculate the concentrations of H+, CH3COO-and CH3COOH at equilibrium. Ka=1.8 x 10-5. CH3COOH=60 g/mol 0.0560 g=9.33 x 10-4mol 9.33 x 10-4mol/0.050 L=0.01867 M CH3COOH CH3COOH CH3COO-H3O+I 0.01867 0 0 C -x +x +x E 0.01867-x x x Ka=[ CH3COO-][ H3O+]/[CH3COOH] X=5.786 x 10-4[H3O+]=[ CH3COO-]=5.786 x 10-4M [CH3COOH]=0.0181 M 2.A titration in conducted where exactly 500 mL of 0.167 M NaOH was titrated into 500 mL 0.100 M CH3COOH. Calculate the pH of the solution at this point in the titration. CH3COOH Ka=1.8 x 10-5. Initial moles NaOH: 0.5 L x 0.167 mol/L=0.0835 mol CH3COOH: 0.5 L x 0.10 mol/L=0.050 mol CH3COOH+ -OH ÆCH3COO-+ H2O All acid is neutralized, 0.0335 mol -OH remaining 0.0335 mol/L=0.0335 M pOH=1.47 pH=12.53
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