Fully answer these questions in your laboratory notebook before coming to lab. S

Question

Fully answer these questions in your laboratory notebook before coming to lab. Show all your for numerical calculations. Define the following terms: a. K_a b. Endpoint c. Equivalence point Why are buffer solutions used to calibrate the pH meters rather than dilute solutions of acids and bases of known concentration? You determine that it takes 18.66 mL of base to neutralize a 25.00 mL sample of your unknown acid solution. The pH of the solution when about 9.33 mL of base had been added was 2.90. You notice that the concentration of the base was 0.1232 M a. What are the K_a and the pK_a of this unknown acid? (Show work.) b. What is a possible identity of this unknown acid? (Use chart in discussion section.) c. What is the concentration of the unknown acid? (Show work.)

Explanation / Answer

Q1.

a)

Ka: = acidic constant/dissociation constant, relates the equilibrium of a weak acid with respect to its dissociation.

It is a measure of how strong/weak a weak acid is.

Example

HA(aq) <-> H+(aq) + A-(aq)

Ka = [H+][A-]/[HA]

note that if Ka is high, then expect high amonut of H+ and A-

if Ka is low, then HA is higher, therefore, least strong

b)

Endpoint = the point in which we assume the titration must end. It is usually pretty near to the equivalence point, in which our indicator changes color.

c)

Equivalence point = the point in which amount of acid = amount of base

therefore, it is a very important point, specially for analytical chemistry and titration chemistry

Related Questions

Navigate

• Browse (All)
• Browse F
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.