General Characteristics Acids and Bases General Characteristics

Originally, chemists classified substances as acids or bases based on properties that were easily observed without the advanced lab equipment of today They did this using aqueous solutions of the compounds in question

Common Characteristics of Acids In aqueous solution. . . have a sour taste react with bases to produce salts and water (next lesson) change the color of acid/base indicators react with metals to produce hydrogen gas conduct electric current

Common Characteristics of Bases In aqueous solution. . . have a bitter taste change the color of acid/base indicators feel slippery react with acids to produce salt and water (next lesson) conduct electric current

Binary Acid nomenclature a binary acid contains two different elements- one of which is hydrogen hydro + root of second element + ic example: HCl hydro + chlor + ic = hydrochloric try naming HF on your own

Oxoacid Nomenclature Oxoacids: contain oxygen in addition to Hydrogen If the oxyacid contains more than one O, use the following rules. addition of one O atom to “-ic” acid: name “per…-ic” acid Ex. HClO3 = chloric acid HClO4 = perchloric acid removal of one O atom from “-ic” acid: name “-ous” acid -Ex. HClO2 = chlorous acid removal of 2 O atoms from “-ic” acid: name “hypo…-ous” acid -Ex. HClO = hypochlorous acid

As we mentioned before, acids and bases conduct electricity in solution, so they must ionize example HCl  H+ + Cl-

Definition of Acids and Bases Svante Arrhenius defined acids and bases as acid: substance that ionizes in water and increases the number of hydrogen ions base: substance that ionizes in water and increases the number of hydroxide ions (OH-)

Hydrogen ions don’t last very long in water they react immediately with water to form hydronium ions H+ + H2O  H3O+

Acid Strength Strong acids ionize completely in water they are completely soluble Weak acids do not ionize completely in water they are only partially soluble Refer to table on page 501 (Blue Book) page 483 (Red Book)

Bases bases can increase hydroxide ion concentration in two different ways ionization to form OH- ions NaOH  Na+ + OH- reaction with water to make OH- NH3 + H2O  NH4+ + OH- Base strength- refer to table on page 501 (Blue) page 483 (Red)

2. Bronsted-Lowery Definition Second conceptual definition Designed separately by two different scientists Look at the H atom and the H+ ion e- e- H+ is actually just a proton p+ p+ H H+ a. Acids - a Bronsted-Lowery acid is a compound which releases a proton H+ H+ H+ H+ - HCl + H2O  H3O+ + Cl- H Cl H3O+ H2O HCl gives a proton to H2O, HCl is an acid proton donor

b. Base A Bronsted – Lowery base is a compound which accepts a proton H+ H+ H+ H+ - HCl + H2O  H3O+ + Cl- H Cl H3O+ H2O H2O accepts a proton. It is a base by B/L standards proton acceptor Examples – For each of the reactants, list the Bronsted Lowery acid and base 1. H3O+ + OH-  2 H2O 2. Cl- + H3O+  HCl + H2O 3. NH3 + H2O  NH4+ + OH- acid base base acid base acid

c. Amphiprotic/Amphoteric substances HCl + H2O  H3O+ + Cl- Water is a base NH3 + H2O  NH4+ + OH Water is an acid Water is both an acid and a base Amphiprotic/Amphoteric substances Can be either an acid or a base under different conditions Will appear on both sides of chart L d. Conjugate Acid/Base pairs Many acid/base reactions are reversible HCl + H2O H3O+ + Cl- acid base HCl + H2O H3O+ + Cl- acid base HCl + H2O H3O+ + Cl- When HCl becomes Cl-, it can now act as a base HCl is an acid Cl- is a base

Conjugate Acid/Base Pairs Acid and base differ only by one proton Acid Has extra proton Base Missing a proton base acid acid base NH3 + H2O NH4+ + OH- Example 1. Indicate the conjugate acid/base pairs of the following H2O + HNO3 H3O+ + NO3- CO3-2 + H2O OH-+ HCO3- base base acid acid base acid base acid

C. Strength of Conjugate Acid/Base Pairs If the acid is strong, its conjugate base is weak, and vice versa HCl + H2O H3O+ + Cl- Strong acid Strong base Weak base Weak acid Strong acid Strength of Acids chart - acids side The higher acid is the stronger one Bases side The LOWER base is the stronger one Acids HCl and HSO4- HCl is stronger acid Bases HS- and HCO3- HS- is stronger base Example - Label each as either a stronger acid or base HNO3 + HS- H2S + NO3- Strong base strong strong weak weak acid base acid base