More on conjugate acid-base pairs

MORE ON CONJUGATE ACID-BASE PAIRS: HSO4- (aq) + HOH (aq) ⇄ H3O+ (aq) + SO4 2- (aq) base acid acid base H2CO3 + SO3 2- ⇄ HSO3 - + HCO3 acid base base acid NH3 + NH3 ⇄ acid base NH4+ + NH2acid base NOTE THAT AMMONIA IS ALSO AMPHOTERIC!! WHAT IS THE CONJUGATE BASE FOR: c) HI H3PO4 HSO4- Answers IH2PO4SO4-2 d) H2 H- a) b) WHAT IS THE CONJUGATE ACID FOR: a) b) c) e) HO2SO4-2 Answers H2O2 HSO4- C2H3O2NH2- HC2H3O2 NH3 Note: NEUTRALIZATION: Arrhenius: ACID + BASE ⇄ SALT + WATER Bronsted: ACID + BASE ⇄SALT + SOLVENT! SOME COMMON ACIDS: Chemical name: SULPHURIC ACID Chemical Formula: H2SO4 Commercial/common name: oil of vitriol, battery acid Properties: -cheap to make (raw materials needed are sulphur, oxygen and hydrogen) -good dehydrating agent (removes water from substances) -good neutralizer of bases (strong acid) -strong exothermic reaction when mixed with water -good oxidizing agent -strong electrolyte (this is why it is used in car batteries) Common uses: -fertilizers, explosives, dyes, insecticides, detergents, plastics, car batteries Chemical name: HYDROCHLORIC ACID Chemical Formula: HCl Commercial/common name: muriatic acid Properties: -choking odour in concentrated solutions -good electrolyte -does not produce sulphates with ions, like sulphuric acid does Common uses: -metal oxide cleaners, removing "scale" from kettles, stomach acid, catalysts Chemical name: NITRIC ACID Chemical Formula: HNO3 Commercial/common name: none Properties: -suffocating odour -yellow stain on skin (due to the action of the acid on protein) -very reactive with almost all metals Common uses: -ammonium and phosphate fertilizers, explosives, plastics, dyes, lacquers Chemical name: ACETIC ACID Chemical Formula: CH3COOH Commercial/common name: vinegar (if 5% aqueous solution) Properties: -only affects highly reactive metals -weak electrolyte when diluted Common uses: -food preservation, manufacture of textiles and plastics SOME COMMON BASES: Chemical name: SODIUM HYDROXIDE Chemical Formula: NaOH Commercial/common name: caustic soda, lye Properties: -very corrosive -strong exothermic reaction when mixed with water -good dehydrating agent (RAPIDLY removes water from air) Common uses: -soap, oven cleaner, drain cleaner Chemical name: POTASSIUM HYDROXIDE Chemical Formula: KOH Commercial/common name: caustic potash Properties: -similar to NaOH but lower MP Common uses: -electrolyte in alkaline batteries, liquid soaps (due to lower MP) Chemical name: AMMONIA Chemical Formula: NH3 Commercial/common name: NH3 (aq)  NH4OH is called ammonium hydroxide Properties: -colourless, highly toxic, corrosive gas with strong odour -strong exothermic reaction when mixed with water -very soluble in water Common uses: -manufacture of nitric acid, explosives, fertilizers, synthetic fibers, refrigerant gas ACIDIC AND BASIC ANHYDRIDES AN OXYGEN-CONTAINING COMPOUND THAT REACTS WITH WATER PRODUCING AN ACIDIC SOLUTION IS CALLED AN ACIDIC ANHYDRIDE. eg. SO3 + H2 O  H2SO4 AN OXYGEN-CONTAINING COMPOUND THAT REACTS WITH WATER PRODUCING A BASIC SOLUTION IS CALLED A BASIC ANHYDRIDE. eg. Na2O + H2 O  2NaOH WHEN A BASIC ANHYDRIDE AND AN ACIDIC ANHYDRIDE COMBINE, THEY FORM A SALT. eg. N2 O5 + Na2O  2NaNO3 THE REACTION (as written above) IS A NEUTRALIZATION WITHOUT THE FORMATION OF WATER. N2O5 IS THE ACIDIC ANHYDRIDE OF HNO3 eg. 2HNO3  N2 O5 + H2 O acid anhydride water ANHYDRIDE MEANS WITHOUT WATER SO A BASIC ANHYDRIDE IS A BASE WITHOUT WATER eg. Ca(OH)2  CaO + H2 O base anhydride water Interesting fact: Grass thrives in alkaline soil. Adding Lime, CaO, increases the alkalinity or basicity of the soil by the following reaction: CaO + H2 O  Ca(OH)2 anhydride water base SOME COMPOUNDS CAN BE AMPHIPROTIC ANHYDRIDES: eg. BeO Al2O3 GeO2 As4O6 Ga2O3 SnO2 Sb4O6 PbO2 STRONG / WEAK / CONCENTRATED / DILUTE STRONG BASE: -any metallic hydroxide which is very soluble in water is a strong base. -if it is not soluble it is a weak base. GROUP I hydroxides: LiOH, NaOH, KOH, RbOH, CsOH, FrOH and also Ca and Ba hydroxides are strong bases: Ca(OH)2 and Ba(OH)2 Other GROUP 2 hydroxides are only slightly soluble & are therefore weak bases. STRONG ACID: -the strongest acid is always the one in which the ionizable hydrogen can be most easily removed HClO4 HI HBr HCl HNO3 H2SO4 PERCHLORIC ACID HYDROIODIC ACID HYDROBROMIC ACID HYDROCHLORIC ACID NITRIC ACID SULPHURIC ACID dissociate ~100% in water at RTP STRONG IS NOT THE SAME AS CONCENTRATED!!! Concentrated: proportion of solute to solvent molecules is near the maximum value (there are a lot of moles of acid/base solute compared to the solvent in the solution) Strong: dissociates well and has MANY ions; favours formation of products (conducts current well) DILUTE IS NOT THE SAME AS WEAK!!! Dilute: low proportion of solute to solvent (nowhere near the max) (not many moles of acid/base relative to solvent in the solution) Weak: dissociates poorly and has FEW ions; favours reactants (conducts current poorly in water) eg. 0.010 M HCl is a dilute strong acid Consider: H2SO4 strong acid + 2KOH  strong base K2SO4 + 2H2O neutral salt pH ~7 HCl + strong acid (NH3 (aq)) NH4OH  weak base NH4Cl + H2O acidic salt pH <7 3HC2H3O2 weak acid + Fe(OH)3  Fe(C2H3O2)3 + 3H2O weak neutral base salt pH ~7 H2CO3 weak acid + 2KOH  strong base K2CO3 + 2H2O basic salt pH >7 Strongest acid in water: hydronium ion Strongest base in water: hydroxide ion ALL OF CHAPTER NINE HAS BEEN COMPLETED!!! NOW DO WORKSHEET 4.2 FOR HOMEWORK Wkst 4.2: Arrhenius and Brønsted-Lowry Acids Using Brønsted-Lowry definitions, identify… a) the missing conjugate… ACID BASE F ACID - BASE HPO4-2 SO3-2 H2O NH3 HNO2 HCO3 - PH4 H2O + HC2O4 - b) the ACID-BASE conjugate pairs in the following reactions… - HBr + Cl CO3-2 + H2O + H3O + HSO4 + NH3 + PH2 HS - HSO3 - HNO2 HS2O3 - + - - - + Br + OH H2S + H2O  H2SO3 + SO4-2  NH4 + NO2  PH3 + S2O3-2  HCl  HCO3  - + - - c) Neutralization and salt pH Salt pH HCl(aq) + strong acid Cu(OH)2(aq)  H2O(l) + weak base CuCl2(aq) Acidic salt H3PO4(aq) + NaOH(aq)  + H2CO3(aq) + Pb(OH)4(aq)  + H2SO4(aq) + Fe(OH)3(aq)  + HClO4(aq) + LiOH(aq)  + +  H2O(l) + ZnI2(aq) +  H2O(l) + AlF3(aq) +  H2O(l) + KBr(aq) pH<7 Wkst 4.2: Arrhenius and Brønsted-Lowry Acids Using Brønsted-Lowry definitions, identify… a) the missing conjugate… ACID BASE HF F HPO4-2 PO4-3 SO3-2 H2O OH + NH3 HNO2 NO2 + PH3 H2CO3 H3O BASE - HSO3 NH4 - ACID HCO3 + - PH4 H2O HC2O4 - - C2O4-2 b) the ACID-BASE conjugate pairs in the following reactions… HBr + Acid + Base + Base  H2O H3O - +  + Acid HS2O3 NH3 -  + PH2 - Base - +  H2S H2SO3 NH4 + + PH3 Acid OH - H2O Base + SO4-2 Base + Acid  - Base Acid Base - HCO3 Br Base Acid Acid HNO2 + Acid + HSO4 HCl Acid Acid Base Acid  Acid - HSO3 - Base CO3-2 HS Cl NO2 - Base + S2O3-2 Base c) Neutralization and salt pH Salt pH 2 HCl(aq) + strong acid H3PO4(aq) + 3 NaOH(aq) + Pb(OH)4(aq) Weak base 3 H2SO4(aq) 2 Fe(OH)3(aq) + Strong acid + + Strong acid  3 H2O(l) + Zn(OH)2(aq) + Al(OH)3(aq)  4 H2O(l) + KOH(aq) Strong base Na3PO4(aq) pH>7 Pb(CO3)2(aq) pH~7 Neutral salt  6 H2O(l) + Fe2(SO4)3(aq) pH<7 Acidic salt  H2O(l) + LiClO4(aq) pH~7 Neutral salt  2 H2O(l) + ZnI2(aq) pH<7 Acidic salt  3 H2O(l) + Weak base + pH<7 Basic salt Weak base Weak acid HBr(aq) LiOH(aq) CuCl2(aq) Acidic salt Strong base Strong acid 3 HF(aq) + Weak base Strong acid 2 HI(aq) 2 H2O(l) Strong base Weak acid HClO4(aq)  weak base Weak acid 2 H2CO3(aq) Cu(OH)2(aq) AlF3(aq) pH~7 Neutral salt  H2O(l) + KBr(aq) Neutral salt pH~7