The Acid-Base Properties of Water

Practice Problem A What is (a) the conjugate acid of CIO4, (b) the conjugate acid of, (c) the 

Practice Problem B HSO3 is the conjugate acid of what species HSO3 is the conjugate base of what species  

Label each of the species in the following equations as an acid, base, conjugate base, or conjugate acid  

Strategy In each equation, the reactant that loses a proton is the acid and the reactant that gains a proton is the base. Each product is the conjugate of one of the reactants. Two species that differ only by a proton constitute a conjugate pair. 

Setup (a) HF loses a proton and becomes F NH3 gains a proton and becomes NH J. 

Practice Problem A Identify and label the species in each reaction. 

Strategy Remember that a conjugate base always has one fewer H atom and one more negative charge (or one fewer positive charge) than the formula of the corresponding acid. 

Practice Exercise Identify the conjugate acid-base pairs for the reaction CN -I- H2O HCN + OH  

Which of the following does not constitute a conjugate acid-base pair (a) HNO2-NO2. (b) H2C03-C01 . (c) CH3NH -CH3NH2. 

It is acceptable to represent the proton in aqueous solution either as or as HsO. The formula is less cumbersome in calculations involving hydrogen ion concentrations and in calculations involving equilibrium constants, whereas is more useful in a discussion of Brpnsted acid-base properties. 

as we know, is a unique solvent. One of its special properties is its ability to act either as an acid or as a base. Water functions as a base in reactions with acids such as HCl and CH3COOH, and it functions as an acid in reactions with bases such as NH3. Water is a very weak electrolyte and therefore a poor conductor of electricity, but it does undergo ionization to a small extent  

Tap water and water from underground sources do conduct electricity because they contain many dissolved ions. 

The acid-base conjugate pairs are (1) H2O (acid) and OH (base) and (2) HgO (acid) and H2O (base). 

In the study of acid-base reactions, the hydrogen ion concentration is key its value indicates the acidity or basicity of the solution. Because only a very small fraction of 

Reaction between two water molecules to form hydronium and hydroxide ions. 

---

This reaction is sometimes called the autoionization of water. To describe the acid-base properties of water in the Brpnsted framework, we express its autoionization as follows (also shown in Figure 15.1) ... 

THE ACID-BASE PROPERTIES OF WATER Review Questions... 

See the Saunders Interactive General Chemistry CD-ROM, Screen 1 7.3, The Acid-Base Properties of Water. 

The acid—base properties of water, together with its solvent polarity, mean that free charged groups (ions) are common, and most biological macromolecules must be regarded as polyelectrolyes large molecules with multiple charges. 

The acid-base properties of water play an important part in biological processes because of the central role of water as a solvent. The extent of self-dissociation of water to hydrogen ion and hydroxide ion. 

Next, we examine the acid-base properties of water and define the ion-product constant for the autoionization of water to give H and OH ions. (15.2)... 

---