Humboldt State University ® Department of Chemistry

Richard A. Paselk


General Chemistry

Spring 2009

Exercise: Chemical Equilibrium

© R. Paselk 2008

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Chemical Dissociation Equilibrium Problems

1. What is the concentration of hydrogen ion in a 0.20 M solution of acetic acid (CH3COOH) if Ka = 1.8 x 10-5 @ 25°C? ( Ka is the equilibrium constant for an acid dissociation.)

2. Calculate the solubility of calcium carbonate. CaCO3 is used by organisms to make shells etc. Vast deposits of these shells make up limestone and (after heat and compression) marble deposits. An important consideration in determining whether shells can be formed, limestone deposited etc. is the solubility of calcium carbonate. For the reaction of solid calcium carbonate in equilibrium with its ions, K = 8.7 x 10-9.

3. When excess solid lead(II) chloride is dissolved in water at 25°C the equilibrium concentration of lead(II) ion is found to be 1.62 x 10-2 M. Calculate the equilibrium constant for this reaction giving a saturated solution.

4. What is the solubility of ferric hydroxide in a buffered aqueous solution where [OH-] = 1 x 10-6M. For the reaction of solid ferric hydroxide in equilibrium with its ions, K = 4 x 10-38.

Answers 1-4

In addition to these exercises you should work on the text materials.

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© R A Paselk

Last modified 23 November 2009