Presentation on theme: "Acids and Bases Chapters 20-21. Properties of Acids Sour taste Change the color of dyes known as acid-base indicators (turns litmus red) React with bases."— Presentation transcript:
Acids and Bases Chapters 20-21
Properties of Acids Sour taste Change the color of dyes known as acid-base indicators (turns litmus red) React with bases to produce a salt (ionic compound) and water Electrolytes (aqueous solutions will conduct electric current) Can react with active metals to give off hydrogen gas (H 2 )
Definitions of Acids Lewis: atom or molecule that is an electron-pair acceptor (H + ) Arrhenius (traditional): compound that contains hydrogen and ionizes in solution to form hydrogen ions (H + ) (H + )Bronsted-Lowry: molecule or ion that is a proton (H + ) donor
Number of Protons in Acids Monoprotic acids can donate one H + ion per molecule HCl, HNO 3, HBr, HClO 4 Examples: HCl, HNO 3, HBr, HClO 4 Diprotic acids can donate two H + ions per molecule H 2 SO 4, H 2 Se Examples: H 2 SO 4, H 2 Se Triprotic acids can donate three H + ions per molecule H 3 PO 4 Example: H 3 PO 4 Polyprotic acids can donate more than one H + ion per molecule H 2 SO 4 H + + HSO 4 - HSO 4 - H + + SO 4 2-
Hydronium Ion hydronium ion(H 3 O + )The terms hydrogen ion (H + ), proton (p + ), and hydronium ion (H 3 O + ) are used interchangeably H 3 O +Hydrogen ion (H + ) in an aqueous solution (H 2 O) becomes H 3 O + H 3 O + hydronium ionH 3 O + is known as a hydronium ion
Naming Acids (Review) OxyacidsOxyacids two elements contains more than two elements (H, O, and 3 rd element) (a cation, H +, and a polyatomic anion with O) Binary AcidsBinary Acids two elements contain two elements (a cation, H +, and a monatomic anion) hydro______ic acid ________ous acid(-ite ion goes with –ous ending) ________ic acid(-ate ion goes with –ic ending)
Oxyacid Naming Series per______ic acid most oxygens ______ic acid goes with –ate anion ______ous acid goes with –ite anion hypo______ous acid least oxygens
Properties of Bases Bitter taste Change the color of dyes known as acid-base indicators (turns litmus blue) salt (ionic compound) and waterReact with acids to produce a salt (ionic compound) and water ElectrolytesElectrolytes (aqueous solutions will conduct electric current) slipperyFeel slippery to the skin Basic substances are referred to being alkaline."
Definitions of Bases Lewis: atom or molecule that is an electron- pair donor Arrhenius (traditional): compound that contains hydroxide and dissociates in solution to form hydroxide ions (OH - ) Bronsted-Lowry: molecule or ion that is a proton (H + ) acceptor
Naming Bases (Review) Name as ionic compound Cation anionCation named first, anion named second Potassium Chloride KCl PbSn (Zn, Ag, and Cd dont need Roman numerals.)All transition metals and Pb and Sn need Roman numerals to denote their charge. (Zn, Ag, and Cd dont need Roman numerals.) –ide monatomic anion.Change ending of all nonmetals to –ide to name their monatomic anion. Polyatomic ionsPolyatomic ions must be memorized! Review them if you have forgotten.
Name the Following: 1.H 3 PO 4 2.Ba(OH) 2 3.HClO 2 4.H 3 N 5.Al(OH) 3 6.HIO 3 7.H 2 SO 3 8.HBr 9.Cu(OH) 2 10.H 2 S phosphoric acid barium hydroxide chlorous acid hydronitric acid aluminum hydroxide iodic acid sulfurous acid hydrobromic acid copper (II) hydroxide hydrosulfuric acid
Neutralization Acid + Base Ionic Compound + H 2 O The ionic compound formed from the reaction of an acid and a base is known as a salt. It is formed from the cation of the base and the anion of the acid. The cation from the acid (H + ) and the anion from the base (OH - ) form the water Hydrolysis: reaction between water and ions of a dissolved salt; causes water to dissociate into H + and OH - ions
Write balanced equations: barium hydroxide solution mixed with phosphoric acid aqueous sodium hydroxide neutralized with hydrochloric acid aluminum hydroxide solution mixed with chloric acid sulfuric acid reacted with aqueous magnesium hydroxide
Answers: 3 Ba(OH) 2 (aq) + 2 H 3 PO 4 (aq) Ba 3 (PO 4 ) 2 (s) + 6 H 2 O ( l ) NaOH (aq) + HCl (aq) NaCl (aq) + H 2 O ( l ) Al(OH) 3 (aq) + 3 HClO 3 (aq) Al(ClO 3 ) 3 (aq) + 3 H 2 O ( l ) H 2 SO 4 (aq) + Mg(OH) 2 (aq) MgSO 4 (aq) + 2 H 2 O ( l )
Info for Hydrolysis Worksheet strong acids (ionize 100% in solution): HClO 4, HNO 3, H 2 SO 4, HI, HBr, HCl strong bases (ionize 100% in solution): Hydroxides of Groups 1 and 2 on Periodic Table If theyre not strong, we assume they are weak!
Bronsted-Lowry Conjugate Acid-Base Pairs Acid: H + donor Remember, B-L Acid: H + donor Base: H + acceptor B-L Base: H + acceptor conjugate acid(conjugate base) When an acid is dissolved in water, the acid (HA) donates a proton to water to form a new acid (conjugate acid) and a new base (conjugate base) HA (aq) + H 2 O ( l ) H 3 O + (aq) + A - (aq) acid base conjugate acid conjugate base H+H+ H+H+
Bronsted-Lowry Acid Conjugate Base HA HCl HNO 3 H 2 SO 4 HSO 4 - H 3 O + H 2 O A - Cl - NO 3 - HSO 4 - SO 4 -2 H 2 O OH -
A few more items: Amphoteric: any species that reacts as either an acid or a base weak conjugate basesstrong acids have weak conjugate bases strong conjugate basesweak acids have strong conjugate bases strong acids (ionize 100% in solution): HClO 4, HNO 3, H 2 SO 4, HI, HBr, HCl strong bases (ionize 100% in solution): Hydroxides of Groups 1 and 2 on Periodic Table
pH notes The pH scale ranges from 0 to 14.The pH scale ranges from 0 to 14. pH below 7 acid Any substance with a pH below 7 is classified as an acid base. Any substance with a pH above 7 is classified as a base. pH of 7 Substances with a pH of 7 are said to be neutral. (Pure water has a pH of 7.) __________________________________________________________________________ | | | | | | | | | | | | | | | neutral strong acid weak acid neutral weak base strong base
Titration Titration is the method used to determine the concentration of a solution (usually an acid or base). A solution of known concentration (the standard) is added to a measured amount of the solution of unknown concentration until an indicator signals the endpoint. The endpoint occurs when equivalent amounts of H + and OH - have reacted in a titration, thus neutralizing the resultant solution.
Indicators changes in pH hydronium ion concentrationAcid-base indicators are dyes used in titrations whose colors are sensitive to changes in pH, or hydronium ion concentration. neutralizationThere are many indicators, each indicative of a different pH range. For most titrations, a neutralization reaction is desired. For a strong acid and strong base, the chosen indicator will change near the neutral point at a pH of 7. Examples:phenolphthalein pink in base bromothymol blue yellowblueExamples: phenolphthalein (changes from clear in acid to pink in base) and bromothymol blue (changes from yellow in acid to blue in base)
Sample Titration 50. mL of 0.1 M HCl50. mL of 0.1 M HCl when titrated with 0.1 M NaOH50. mL0.1 M NaOH should take just over 50. mL to cause a color change monoprotic strong acid group I hydroxide strong base.because it is a monoprotic strong acid being neutralized by a group I hydroxide strong base. pH of 7(For this titration, we would choose an indicator that changed color at a pH of 7 or neutral to indicate that the acid had been fully neutralized by the added base.) 0.1 M H 2 SO 4 H + ion diprotic acid0.1 M H 2 SO 4 substituted in the above problem would have a different effect since the H + ion concentration would change for a diprotic acid
Titration Equation M a V a = M b V b [H + ] = [OH - ]In titrations between acids and bases, neutralization is required so the [H + ] = [OH - ] In order to take this into account, our equation becomes n b M a V a = M b V b n a # of H + ions in base # of OH - ions in acid Molarity of acid Molarity of base volume of acid volume of base