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General Chemistry Principles, Patterns, and Applications, 2011

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Equation 16.10: [H + ] = 10 −pH<br />

Definition of pOH<br />

Equation 16.11: pOH = −log 10[OH + ]<br />

Equation 16.12: [OH − ] = 10 −pOH<br />

Relationship among pH, pOH, <strong>and</strong> p K w<br />

Equation 16.13: pK w= pH + pOH<br />

C O N C E PTUAL P R OBLEMS<br />

1. What is the relationship between the value of the equilibrium constant for the autoionization of liquid water<br />

<strong>and</strong> the tabulated value of the ion-product constant of liquid water (K w )?<br />

2. The density of liquid water decreases as the temperature increases from 25°C to 50°C. Will this effect<br />

cause K w to increase or decrease? Why?<br />

3. Show that water is amphiprotic by writing balanced chemical equations for the reactions of water with<br />

HNO 3 <strong>and</strong> NH 3 . In which reaction does water act as the acid? In which does it act as the base?<br />

4. Write a chemical equation for each of the following.<br />

a. Nitric acid is added to water.<br />

b. Potassium hydroxide is added to water.<br />

c. Calcium hydroxide is added to water.<br />

d. Sulfuric acid is added to water.<br />

5. Show that K for the sum of the following reactions is equal to K w .<br />

a.<br />

a. HMnO4 aq<br />

( ) H + ( aq) + MnO4 - ( aq)<br />

A N S W E R S<br />

1.<br />

K auto = [H 3 O + ][OH − ]/[H 2 O] 2 K w = [H 3 O + ][OH − ] = K auto [H 2 O] 2<br />

2.<br />

3. H 2 O(l) + HNO 3 (g) → H 3 O + (aq) + NO − 3 (aq); water is the baseH 2 O(l) + NH 3 (g) → OH − (aq) +<br />

NH − 4 (aq); water is the acid<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

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