3 6 Acids and Bases 0 1 M HCl in stomach Drano solid NaOH with some Al chips Organic acids carboxylic acids occur in nature acetic acid vinegar There are 2 most commonly used definitions of acids and bases 1 Arrhenius 2 Bronsted Lowry 1 Acids and Bases The Arrhenius Definition An acid is a substance that when dissolved in water increases the concentration of H ions in solution So if it makes an H then it is an acid HCl H ClA base is a substance that when dissolved in water increases the concentration of OH ions in solution So if it makes an OH it is a base NaOH Na OH2 Strong acids the ones that ionize completely have to memorize those HCl HBr HI HNO3 H2SO4 HClO4 Weak acids any acids that are not strong don t ionize completely no need to memorize those 3 Strong bases ionize completely need to memorize those LiOH NaOH KOH Ba OH 2 Sr OH 2 Weak bases ionize less than 100 4 5 Table 3 1 p 129 Acids and Bases The Bronsted Lowry Definition An acid is a proton donor A base is a proton acceptor An acid base reaction involves the transfer of a proton from an acid to a base to form a new base and a new acid The reaction is written as an equilibrium reaction and the equilibrium favors the weaker acid and base 6 7 8 Amphiprotic a molecule species can act as an acid and a base Examples 9 Reactions of Acids and Bases Acids and bases react to produce a salt and water Neutralization reaction Do complete ionic net ionic 10 Acetic acid potassium hydroxide 11 Phosphoric acid plus lithium hydroxide 12 Ammonia nitric acid 13 Oxides of Nonmetals and Metals Oxides of nonmetals react with H2O to form weak acids Oxides of nonmetals called acidic oxides 14 Oxides of metals are called basic oxides because they give basic solutions if they dissolve in water CaO s H2O l Ca OH 2 aq 15 3 7 Gas Forming Reactions Form a gas Recognizing gas forming reactions H2CO3 decomposes to CO2 and H2O H2SO3 decomposes to SO2 and H2O H2S gaseous product NH4 and OH ions form NH3 gas and water 16 Calcium carbonate hydrochloric acid 17 Calcium carbonate and acetic acid 18 19 Table 3 2 p 136 3 8 Oxidation Reduction Reactions Redox reactions Always occur together Can t have one without the other Mnemonic device OIL RIG or LEO GER 20 Oxidation is an increase in the oxidation number Corresponds to the loss of electrons Reduction is a decrease in the oxidation number Good mnemonic reduction reduces the oxidation number Corresponds to the gain of electrons Oxidation and reduction occur simultaneously in all reactions often called redox reactions 21 Oxidizing agents are chemical species that 1 oxidize some other substance 2 contain atoms that are reduced in the reaction 3 gain electrons Reducing agents are chemical species that 4 reduce some other substance 5 contain atoms that are oxidized in the reaction 6 lose electrons KNOW this 22 Oxidation Numbers Most common oxidation numbers 23 Oxidation numbers Guidelines for assigning oxidation numbers 1 Each atom in a pure element has an oxidation of 0 2 For monatomic ions the ox charge on ion 3 When combined with another element F always has an oxidation of 1 4 Oxygen is 2 in most compounds except peroxides where it is 1 or superoxides 1 2 5 Cl Br I are usually 1 except when combined with O and F 6 H is mostly 1 unless it is a hydride then 1 example CaH2 7 Oxidation have to add to 0 if compound is neutral or to charge on polyatomic ion 24 Assigning oxidation 25 2 Mg s O 2 g 2 MgO s What is oxidized reduced ox agent red agent of e transferred 26 Write and balance the formula unit complete ionic and net ionic equations for the oxidation of sulfurous acid to sulfuric acid by oxygen in acidic aqueous solution What is reduced oxidized reducing agent ox agent etc 27 Recognizing Oxidation Reduction Reactions Easiest way assign oxidation to all elements and compounds if they changed from reactants to products then it is a redox reaction 28 Zn HCl H2 ZnCl2 Balance first 29 Combustion Reaction Complete combustion enough O2 present produces carbon dioxide and water Incomplete combustion not enough O2 present produces carbon monoxide and water CH4 O2 CO2 H2O CH4 O2 CO H2O 30 Miscible a liquid is miscible in another if they both have similar intermolecular forces e g alcohol and water gasoline and oil Immiscible a liquid is immiscible in another if they have dissimilar intermolecular forces e g water and gasoline oil and water Italian dressing Alkyl alcohols up to 4 C miscible in water 31 3 9 Classifying Reactions in Aqueous Solution We discussed 4 types of reactions Precipitation reaction Acid base reaction Gas forming reaction Oxidation reduction reaction 32