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11 Dec 2019

Which of the follow statements is FALSE?

a Group 1A and Heavy Group 2A metal hydroxides are classified as strong bases.
b When a strong acid dissolves in water it ionizes completely.
c When a weak acid dissolves in water it ionizes completely.
d The conjugate of a strong base is a negligible conjugate acid.
e When a strong base dissolves in water it ionizes completely.

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Lelia Lubowitz
Lelia LubowitzLv2
13 Dec 2019

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Related questions

For conjugate acid-base pairs, how are Ka and Kb related?

Consider the reaction of acetic acid in water.

 

where  

a. Which two bases are competing for the proton?

b. Which is the stronger base?

c. In light of your answer to part b, why do we classify the acetate ion (CH3CO2-) as a weak base? Use an appropriate reaction to justify your answer.

In general, as base strength increases, conjugate acid strength decreases. Explain why the conjugate acid of the weak base NH3 is a weak acid.

To summarize, the conjugate base of a weak acid is a weak base and the conjugate acid of a weak base is a weak acid (weak gives you weak). Assuming Ka for a monoprotic strong acid is 1x106, calculate Kb for the conjugate base of this strong acid. Why do conjugate bases of strong acids have no basic properties in water? List the conjugate bases of the six common strong acids. To tie it all together, some instructors have students think of Li+, K+, Rb+, Cs+, Ca2+, Sr2+, and Ba2+ as the conjugate acids of the strong bases LiOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, and Ba(OH)2. Although not technically correct, the conjugate acid strength of these cations is similar to the conjugate base strength of the strong acids. That is, these cations have no acid properties in water; similarly, the conjugate bases of strong acids have no basic properties (strong gives you worthless). Fill in the blanks with the correct response. The conjugate base of a weak acid is a ______ base. The conjugate acid of a weak base is a ______ acid. The conjugate base of a strong acid is a ______ base. The conjugate acid of a strong base is a ______ acid. (Hint: Weak gives you weak and strong gives you worthless.)

For conjugate acid-base pairs, how are Ka and Kb related?

Consider the reaction of acetic acid in water:

CH3CO2H (aq) + H2O (l) ⇌ CH3CO2− (aq) + H3O+ (aq)             where Ka = 1.8 × 10−5

  1. Which two bases are competing for the proton?
  2. Which is the stronger base?
  3. In light of your answer to part b. why do we classify the acetate ion (CH3CO2−) as a weak base? Use an appropriate reaction to justify your answer.
  4. In general, as base strength increases, conjugate acid strength decreases. Explain why the conjugate acid of the weak base NH3 is a weak acid.

 

To summarize, the conjugate base of a weak acid is a weak base and the conjugate acid of a weak base is a weak acid (weak gives you weak). Assuming Ka for a monoprotic strong acid is 1× 106, calculate Kb for the conjugate base of this strong acid.

Why do conjugate bases of strong acids have no basic properties in the water?

List the conjugate bases of the six common strong acids.

To tie it all together, some instructors have students think of Li+, K+, Rb+, Cs+, Ca2+, Sr2+, and Ba2+ as the conjugate acids of the strong bases LiOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, and Ba(OH)2. Although not technically correct, the conjugate acid strength of these cations is similar to the conjugate base strength of the strong acids. That is, these cations have no acidic properties in water; similarly, the conjugate bases of strong acids have no basic properties (strong gives you worthless). Fill in the blanks with the correct response. The conjugate base of a weak acid is a_____base. The conjugate acid of a weak base is a_____acid. The conjugate base of a strong acid is a_____base. The conjugate acid of a strong base is a_____ acid. ( Hint: Weak gives you weak and strong gives you worthless.)

Unlike strong acids and bases that ionize completely in solution, weak acids or bases partially ionize. The tendency of a weak acid or base to ionize can be quantified in several ways including

Ka or Kb,

pKa or pKb,

and percent ionization*.

*This assumes that species of equal concentrations are being compared as percent ionization is affected by concentration.

Part A

Pyridine is a weak base that is used in the manufacture of pesticides and plastic resins. It is also a component of cigarette smoke. Pyridine ionizes in water as follows:

C5H5N+H2O⇌C5H5NH++OH−

The pKb of pyridine is 8.75. What is the pH of a 0.400 M solution of pyridine? (Assume that the temperature is 25 ∘C.)

Express the pH numerically to two decimal places.

Part B

Benzoic acid is a weak acid that has antimicrobial properties. Its sodium salt, sodium benzoate, is a preservative found in foods, medications, and personal hygiene products. Benzoic acid ionizes in water:

C6H5COOH⇌C6H5COO−+H+

The pKa of this reaction is 4.2. In a 0.80 M solution of benzoic acid, what percentage of the molecules are ionized?

Express your answer to two significant figures and include the appropriate units.

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