5.1 Acids and Bases. Acids. Naming Acids. NEVER try to identify an acid or base by taste or touch!

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1 5.1 Acids and Bases Acids and bases are very common. Acids and bases can be very dangerous and corrosive! NEVER try to identify an acid or base by taste or touch! Acids Acids often behave like acids only when dissolved in water. - so are often written with the subscript (aq) = aqueous = water The chemical formula of an acid usually starts with Hydrogen (H). - One exception to know: CH 3 COOH (aq) (acetic acid) Naming Acids There are 3 types of acid naming: 1) Acids with an anion ending in ide Hydrogen + -ide Hydro ic acid Ex. HF (aq) = hydrogen fluoride = hydrofluoric acid 2) Acids with an anion ending in ate Hydrogen + -ate ic acid Ex. H 2 CO 3(aq) = hydrogen carbonate = carbonic acid 1

2 Bases 3) Acids with an anion ending in ite Hydrogen + -ite ous acid Ex. H 2 SO 3(aq) = hydrogen sulphite = sulphurous acid Bases, like acids, often behave like bases only when dissolved in water - so, they are also often written with the subscript (aq) = aqueous = water The chemical formula of a base usually ends with hydroxide (-OH). Examples of common bases: NaOH (aq), Mg(OH) 2(aq), Ca(OH) 2(aq), NH 4 OH (aq) Production of Ions Acids and bases can conduct electricity because they release ions in solution. - Acids release hydrogen ions, H + (aq) - Bases release hydroxide ions OH (aq) The ph of a solution relates to the concentration of ions it has. Square brackets are used to signify concentration, [H + (aq)], [OH (aq)] High [H + (aq)] = low ph, very acidic High [OH (aq)] = high ph, very basic A solution cannot have BOTH high [H + (aq)] and [OH (aq)]; they cancel each other out and form water. This process is called neutralization. H + (aq) + OH (aq) H 2 O (l) 2

3 ph Scale The strength of acids and bases is measured on the ph scale ph below 7 = acidic ph 7 = neutral ph above 7 = basic Acids Neutral Bases Each decrease of 1 on the ph scale indicates 10X more acidic For example, ph 4 is ten times more acidic than ph 5 ph 3 is 1000X more acidic than ph6 ph Indicators ph is measured by 1) chemicals called indicators, or 2) by a ph meter - it measures the electrical conductivity of the solution using electrical probes to measure how solutions conduct electricity. ph indicators change colour based on the solution they are placed in. Litmus paper is the most common indictor. Two colours of litmus paper: Blue = basic (>7) and Red = acidic (<7). 5.2 Salts ionic compounds formed when acids & bases react OR when oxides or carbonates react with acids OR when metals react with acids. Table salt, (NaCl) is only one kind of salt: is found in seawater, salt lakes or rock deposits. Salts are found in many things: batteries, explosives, fertilizers, multivitamins and many living cells Salt crystals in Death Valley Acid-Base Neutralization Neutralization reactions occur when an acid and a base react to produce a salt and water. HCl (aq) + NaOH (aq) NaCl (s) + H 2 O (l) acid base salt water Metal Oxides react with water to form bases. (MOB) Na 2 O (s) + H 2 O (l) 2NaOH (aq) 3

4 Non-Metal Oxides Acids and Metals react with water to form acids (NOA) SO 2(g) + H 2 O (l) H 2 SO 3(aq) Non-metal oxides are formed from burning fossil fuels water in the atmosphere + non-metal oxides = acid rain The most reactive metals, at the bottom of groups 1 and 2, react vigorously with acids. All other metals are less reactive than those in groups 1 and 2. When metals do react with acids, H 2 gas is usually released 2HCl (aq) + Mg (s) MgCl 2(s) + H 2(g) The effects of acid rain on a forest Acids and Carbonates 5.3 Organic Compounds Carbonates (-CO 3 ) neutralize acids, protecting locations with natural carbonate supplies from acid precipitation. H 2 SO 4(aq) + CaCO 3(s) CaSO 4(s) + H 2 O (l) + CO 2(g) sulphuric calcium calcium water carbon acid carbonate sulphate dioxide Organic compounds contain carbon, and usually hydrogen. Organic sounds like the compounds come from living things, but some do, and some don t. Inorganic compounds do not have carbon (as well as some exceptions: CO 2, CO and ionic carbonates) 4

5 Why Carbon? It has four valence electrons, which allows for more chemical bonding possibilities than other elements. Long chains of carbon can form Examples: petroleum and plastics Hydrocarbons: Alcohols: organic compounds that contains only carbon and hydrogen. Hydrocarbons are based on a carbon backbone, or chain, with hydrogen atoms added on the sides. The simplest hydrocarbons are methane (CH 4 ), ethane (C 2 H 6 ), propane (C 3 H 8 ), butane (C 4 H 10 ), and pentane (C 5 H 12 ) All hydrocarbons are flammable, and most are liquids at room temperature are organic compounds with an -OH group off of the carbon chain. The simplest alcohols are methanol (CH 3 OH), ethanol (C 2 H 5 OH) and isopropyl alcohol (C 3 H 7 OH). Alcohols are very good solvents (they dissolve other substances) Alcohols are generally very flammable 5

6 Alcohols C OH Some Hydrocarbon Derivatives Halogenated C - X (F, Cl, I or Br) Aldehydes Carboxylic Acids Ethers C - O - C Ketones Esters 6