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12.7 Ostwald’s Dilution Law

Ostwald’s dilution law is a relationship between the dissociation constant and the degree of dissociation of a weak electrolyte (acids, bases)

But concentration C = 1/v

for a weak electrolyte a is very small ( and the law does not apply to strong electrolytes)

\ K = a2C

For a weak acid a =

and a weak base a =

Examples : 1) The dissociation constant of a weak electrolyte is 4 +10- 5 Calculate the degree of dissociation in 0.1 m solution.

2) Calculate the [H+] and degree of dissociation in 0.5 m solution of acetic acid (Ka = 1.8´ 10- 5)

\ a = 6 ´ 10- 3

\a = 6 ´ 10- 3

Now [H+] = a C = 6 ´ 10- 3 ´ 0.5

= 3 ´ 10- 3 m

Index

12.1 - Lowry and Bronsted Concept
12.2 - Conjugate Acid Base Pairs
12.3 - Amphoteric Substance
12.4 - Lewis Acids and Bases
12.5 - Strong and Weak Acids and Bases
12.6 - Dissociation
12.7 - Ostwald's Dilution Law
12.8 - Hydrogen Ion Concentration : pH
12.9 - Polyprotic Acids
12.10 - Salts
12.11 - Methods of Preparation of Salts
12.12 - Properties of Salts

Chapter 13