Question

Volume NaOH added Moles of NaOH added 0.00010 Concentration of NaOH-0.1 M Concentration of HC H10.-01 M a) What is the pH at equivalence point? b) What is the volume of N hat equivalence point? c) Moles of NOH at the equivalence point? d) Moles of HCHO at equivalence point? e) Find K. of HC HO Find pk of HC HO 000220 ellas

Answer 1

(a) At equivalence point the pH of the solution suddenly increases indicating all the acetic acid has been consumed and pH increases only due to excess hydroxide OH^- ions.

From the given data, sudden increase in pH occurs at pH = 9.98

pH at equivalence point = 9.98

(b) volume of NaOH at equivalence point = 30 mL

(c) Moles of NaOH at the equivalence point = 0.00300 mol

(d) Moles of HC₂H₃O₂ at equivalence point = 0.00300 mol

(e) volume of NaOH added to reach equivalence point = 30 mL

volume of NaOH added to reach half-equivalence point = (volume of NaOH added to reach equivalence point) / 2

volume of NaOH added to reach half-equivalence point = (30 mL) / 2

volume of NaOH added to reach half-equivalence point = 15 mL

From the data, when volume of NaOH added is 15 mL, then pH = 4.47

pH at half equivalence point = 4.47

We know that pK_a of weak acid is the pH at half equivalence point

pK_a = pH at half equivalence point = 4.47

pK_a = 4.47

(f) K_a of HC₂H₃O₂ = 10^-pK_a

K_a of HC₂H₃O₂ = 10^-4.47

K_a of HC₂H₃O₂ = 3.4 x 10^-5