Question

Given the following titration curve, which of the statements below are true? (Select all that apply.) Titration of a Polyprotic Acid 12 10 8 ㅎ 6 2 0 0 10 15 20 25 30 35 Volume of NaOH added (m L) a. The 2nd proton is half titrated at 12 mL NaOH added. b. The 1st midpoint occurs at pH about 3.5 c. The 2nd proton requires the same volume of NaOH to titrate as the 1st. d. The 2nd equivalence point is reached with 25 mL NaOH added. e. The 1st equivalence point occurs at a pH about 4.8. Ln

Answer 1

FALSE : The 2 nd proton is half titrated at 12 ml NaOH added.

$\Rightarrow$ The 2 nd proton is half titrated at 18 ml NaOH added i e at second mid point.

FALSE : The 1st mid point occurs at pH about 3.5.

$\Rightarrow$ From scale of graph, it is clear that 1st mid point occurs at pH about 3.0

TRUE : 2nd proton requires same volume of NaOH to titrate as the 1st.

FALSE : 2nd equivalence point is reached with 25 ml NaOH added.

$\Rightarrow$ From graph, it is clear that 2nd equivalence point is reached with 24 ml NaOH added.

TRUE : The 1st equivalence point occurs at about pH =4.8