Autoionization of Water and pH Definition PDF

The Autoionization of Water and the Definition of pH Water is amphoteric: It can act as either an acid or a base This is an incredibly important reaction: The “Kw reaction”.  Autoionization of Water Water is amphoteric; it can...

The Autoionization of Water and the Definition of pH Water is amphoteric: It can act as either an acid or a base This is an incredibly important reaction: The “Kw reaction”.  Autoionization of Water Water is amphoteric; it can act as either an acid or a base. When water acts with itself as an acid and a base to form ions, this process is called autoionization. H2O (l) + H2O (l) ↔ H3O+ (aq) + OH– (aq) Kw = [H3O+] [OH–] = 1.00 × 10−14 at 25 °C All aqueous solutions contain both H3O+ and OH– ions. [H3O+] [OH–] = 1.00 × 10−14 at room temperature always Neutral solutions have equal [H3O+] and [OH–]. [H3O+] = [OH–] = 1.00 × 10−7 M Acidic solutions have a larger [H3O+] than [OH–]. [H3O+] > 1.00 × 10−7 M; [OH–] < 1.00 × 10−7 M Basic solutions have a larger [OH–] than [H3O+]. [H3O+] < 1.00 × 10−7 M; [OH–] > 1.00 × 10−7 M  Describing Acidity: pH The acidity or basicity of a solution is often expressed by pH. pH = −log[H3O+] [H3O+] = 10−pH pH = 7 is neutral. pH < 7 is acidic pH > 7 is basic. pOH = −log[OH−], [OH−] = 10−pOH pH + pOH = 14.0  Complete the entries in the following table [H3O+] [OH-] pH pOH Acidic or basic Solution 1 5.4x10-8 Solution 2 1.8 x 10-10 Solution 3 5.23 The Autoionization of Water and the Definition of pH Homework