CHEM 11b Lecture Notes - Lecture 17: Conjugate Acid, Electronegativity, Oxoacid

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28 Mar 2017

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Document Summary

Acid: a substance that produces h+ ions (protons) in water. Base: a substance that produces oh- ions in water. Acids combine naturally with bases to neutralize each other and form water. A strong acid ionizes completely into protons (h+ ions) and accompanying anions. A weak acid undergoes a reversible reaction with water to ionize only partially. Strong bases are ionic compounds in which the anion is oh-. Amphiprotic and amphoteric means it can be a proton donor and acceptor. Double arrow means the reaction will come to equilibrium because it is reversible. Every bronsted lowry model has two sets of acid-base pairs. Strong acids ionize completely and strong bases dissociate completely. Weak acids and bases only partially ionize in water. Auto-ionization of water = most water is just water but is can have some proton transfers. *dont include liquids or solids when solving for k. [h3o+] = [oh-] = 1. 0 10-7 m (at 25 c)

Related Questions

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

Ka or Kb,

pKa or pKb,

and percent ionization.

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+H2OâC5H5NH++OHâ

The pKb of pyridine is 8.75. What is the pH of a 0.455 M solution of pyridine?

Express the pH numerically to two decimal places.

pH=____________

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 dissociates in water:

C6H5COOHâC6H5COOâ+H+

The pKa of this reaction is 4.2. In a 0.58 M solution of benzoic acid, what percentage of the molecules are ionized?

Express the percentage numerically using two significant figures.

percent ionized = _______________ %

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+H2OâC5H5NH++OHâ

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 âC.)

Express the pH numerically to two decimal places.

Part B

C6H5COOHâC6H5COOâ+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.

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+H2OâC5H5NH++OHâ

The pKb of pyridine is 8.75. What is the pH of a 0.345 M solution of pyridine? (Assume that the temperature is 25 âC .)

Express the pH numerically to two decimal places.

pH=

Part B

C6H5COOHâC6H5COOâ+H+

The pKa of this reaction is 4.2. In a 0.77 M solution of benzoic acid, what percentage of the molecules are ionized?

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

% ionization=

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CHEM 11b Lecture Notes - Lecture 17: Conjugate Acid, Electronegativity, Oxoacid

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