CHEM 001 Lecture Notes - Lecture 20: Hydronium, Nonmetal, Lone Pair

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taupesardine275

17 Sep 2020

School

College of The Sequoias

Department

Chemistry (CHEM)

Course

CHEM 001

Professor

guerra

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Document Summary

Strong acids produce more protons in solution than a weak acid due to the fact that they are almost all completely ionized in solution. Calculations involving strong acids and bases are easy because of this (we assume that they are 100% ionized) Ex: 0. 1m hcl(aq) implies 0. 1m h3o+ and 0. 1m cl-(aq) Weak acids are incompletely ionized in solution, you have to set up an equilibrium equation to calculate the concentrations. Ex: acetic acid only has a dissociation rate of about 1% Bases have a soapy feel (ex: detergent and soap) Water that feels soapy is alkaline due to soft salts. A base in water produces hydroxide ions (oh-) Ex: nh3(aq)+h2o(l) nh +(aq) + oh- (aq) remember that a lone pair donor is considered as a lewis base (usually these are weak bases like nh3, f-, technically the oh- ion is considered as a lewis base) Strong bases are completely ionized in water.

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.

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:

C6H5COOH(aq)+H2O(l)âC6H5COOâ(aq)+H3Oâ(aq)

The pKa of this reaction is 4.2. In a 0.80 mol Lâ1 solution of benzoic acid, what percentage of the molecules are ionized?

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

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

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.

CHEM 001 Lecture Notes - Lecture 20: Hydronium, Nonmetal, Lone Pair

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