Titration of a Diprotic Acid-CHEM 132 Pre-Lab Questions 1. Answer the follow 0.1

Question

Titration of a Diprotic Acid-CHEM 132 Pre-Lab Questions 1. Answer the follow 0.10 M NaOH. regarding the titration of 25.00 mL of a 0.070 M weak acid solution with a. How many ml of 0.10 M NaOH are required to reach the first equivalence point? b. How many total ml of O.10 M NaOH are required to reach the second equivalence point? What is the relationship between the volume of NaOH needed to reach the first and second equivalence points? c. 2. A 0.1310 g sample of an unknown diprotic acid is diluted to 100.00 ml and titrated by using 0.1910 M NaOH. If 14.20 mL of the NaOH solution is required to reach the second equivalence point, what is the molar mass of the acid? 3. Use the titration data in the graph below to calculate K,t and Ks2z. 15 25 10 Volume NaOH (mL) 20 Procedure experiment. Someone in each group will be required to submit a You will be working in pairs for this

Explanation / Answer

Q1.

a)

find mL of NaOh, required for 1st equivalence point

mmol of H+= mmol of OH-

mmol of H+ = 1/2 mmol of acid

mmol of acid = mmol of base

(Macid)(Vacid) = (Mbase)(Vbase)

Vbase = (Macid)(Vacid) /Mbase

Vbase = (0.07)(25) /0.10

Vbase = 17.5 mL of NaOH for 1st equiv. point

b)

find NaOH for 2nd equiv point..

clearly, must be the double or

(Macid)(Vacid) = 2*(Mbase)(Vbase)

Vbase = 2*(Macid)(Vacid) /Mbase

Vbase= 2*25*0.07/0.1

Vbase = 35 mL for 2nd point

c)

ratio between volume of NaOH 1st and 2nd point

ratio = 2nd/1st = 35/17.5 = 2x

or 2:1

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