Question

Problem 4: Consider the titration curves (labeled a and b) for two weak bases, both titrated with 0.100 M HCI. 14 12 10 4 2- 80 100 40 60 0 20 Volume of acid added (mL) a. 14 12 10 4 80 0 20 40 60 100 Volume of acid added (mL) b. 11 What is the initial concentration of hydroxide and hydronium ion in each base solution before the titration starts? 2) Estimate the value of K for each base. a1 What is the volume and pH at the equivalence point for each titration? Work with your group members (alphabetical order): 1) Jalen, Rae, Tori 2) Masya, Ariana, Trenton 3) Diamond, Lauren, Kenya, Cassandra 4) Ahlisa, Jasmin, Jonathan Students in a group should have the same work. All students must turn in their own work. Make copies or take pictures of your work to study for the individual quiz on Tuesday. If all students in a group pass the short quiz on Tuesday (70+) all students in the group receive a 20 % bonus on their total Quiz 7 grade. на

Answer 1

1) The initial ion concentration in each curve is calculated:

a) [H3O +] = 10 ^ -pH = 10 ^ -7 M

[OH-] = 10 ^ -14 / 10 ^ -7 = 10 ^ -7 M

b) [H3O +] = 10 ^ -10 M

[OH-] = 10 ^ -14 / 10 ^ -10 = 10 ^ -4 M

2) The pKb of the base is read, at the midpoint of equivalence of each curve:

a) pKb = 4.2

Kb = 10 ^ -4.2 = 6.3x10 ^ -5

b) pKb = 7.8

Kb = 10 ^ -7.8 = 1.6x10 ^ -8

3) The volumes and pH are read at the equivalence points of each curve:

a) V = 38 mL

pH = 3

b) V = 55 mL

pH = 5

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