Department of Chemistry CHEM1010 General Chemistry *********************************************** Instructor: Dr. Hong Zhang Foster Hall, Room 221 Tel:

CHEM1010/General Chemistry _________________________________________ Chapter 7. (L26)-Acids and Bases Today’s Outline..Review of acids and bases..How to write acid and base molecules in molecular formula..Common acids and bases..Acidic and basic anhydrides nonmetal oxides: Acidic anhydrides metal oxides: Basic anhydrides..Strong acids and strong bases..Weak acids and weak bases

Chapter 7. (L26)-Acids and Bases Chemical properties of acids and bases Chemical properties of acids: -cause litmus indicator dye to turn red (turn blue with base) -taste sour -dissolve active metals (Zn, Fe, Cu, etc.), producing H 2 gas -react with bases to form water and ionic after the DGM loading peak, compounds called salts

Chapter 7. (L26)-Acids and Bases Chemical properties of acids and bases Chemical properties of bases: -cause litmus indicator dye to turn blue (turn red with acid) -taste bitter -feel slippery on the skin -react with acids to form water and ionic compounds called salts

Chapter 7. (L26)-Acids and Bases Acids and bases: The Arrhenius theory -An acid is a molecule that will dissociate into a hydrogen cation (H +, proton) and an anion in an aqueous solution Example:HCl = H + + Cl - -A base is a molecule that will give rise to a hydroxide anion (OH - ) and a cation in an aqueous solution Example: NaOH = Na + + OH - -Neutralization reaction between an acid and a base is: acid + base = salt + water the salt is composed of the cation and anion Example: H 2 SO 4 + 2NaOH = 2H 2 O + 2Na + + SO 4 2-

Chapter 7. (L26)-Acids and Bases Acids and bases: The Bronsted- Lowry acid-base theory According to the Bronsted-Lowry theory: -an acid is a proton donor -a base is a proton acceptor Hydration of proton: H + + H 2 O = H 3 O + H 3 O + is called hydronium ion

Chapter 7. (L26)-Acids and Bases Acids and bases: The Bronsted-Lowry acid-base theory The theory to describe the ionization of HCl: HCl(aq) + H 2 O = H 3 O + + Cl - (aq) The theory to describe the behavior of NH 3 : NH 3 (aq) + H 2 O = NH 4 + (aq) + OH - (aq) The theory to describe the behavior of NaOH: NaOH(aq) + H 2 O = Na + + H 2 O + OH - (aq) H + acceptor

Chapter 7. (L26)-Acids and Bases How to write acid and base molecules in molecular formula..Acids: We commonly put H or proton on the left and the anion on the right (for inorganic acids). Example: HCl, H 2 SO 4, HNO 3..Bases: We commonly put OH on the right and the cation on the left (for inorganic bases). Example: NaOH, Ca(OH) 2

Chapter 7. (L26)-Acids and Bases Co mmon acids..Common acids (see Table 7.1 for more details): NameMolecular FormulaStrength hydrochloric acidHClstrong sulfuric acidH 2 SO 4 strong nitric acidHNO 3 strong phosphoric acidH 3 PO 4 moderate hydrogen sulfate HSO 4 - moderate carbonic acid H 2 CO 3 weak acetic acidCH 3 COOHweak lactic acidCH 3 CHOHCOOHweak boric acid H 3 BO 3 very weak hydrocyanic acidHCNvery weak

Chapter 7. (L26)-Acids and Bases Co mmon bases..Common acids (see Table 7.2 for more details): NameMolecular FormulaStrength sodium hydroxideNaOHstrong potassium hydroxideKOHstrong lithium hydroxideLiOHstrong calcium hydroxideCa(OH) 2 strong* magnesium hydroxideMg(OH) 2 strong* ammoniaNH 3 weak *very low solubility although classified as a strong base

Chapter 7. (L26)-Acids and Bases Acidic and basic anhydrides, nonmetal oxides: Acidic anhydrides Nonmetal oxides can react with water to form acids. These nonmetal oxides are called acidic anhydrides. Example: SO 3 + H 2 O = H 2 SO 4 SO 2 + H 2 O = H 2 SO 3 CO 2 + H 2 O = H 2 CO 3 General form: nonmetal oxide + H 2 O  acid anhydride means without water.

Chapter 7. (L26)-Acids and Bases Acidic and basic anhydrides, metal oxides: Basic anhydrides M etal oxides can react with water to form bases. These metal oxides are called b asic anhydrides. Example: CaO + H 2 O = Ca(OH ) 2 B aO + H 2 O = Ba(OH ) 2 Li 2 O + H 2 O = 2LiOH General form: metal oxide + H 2 O  base

Chapter 7. (L26)-Acids and Bases Strong acids and strong bases Strong acids: Those completely dissociated into proton (H + ) and anion in water solution Example: HCl = H + + Cl - 100% dissociation HNO 3 = H + + NO % dissociation Strong bases: Those completely dissociated into hydroxide (OH - ) and cation Example: NaOH = Na + + OH - 100% dissociation KOH = K + + OH - 100% dissociation

Chapter 7. (L26)-Acids and Bases Weak acids and weak bases Weak acids: Those incompletely or partially dissociated into proton (H + ) and anion in water solution Example: CH 3 COOH = H + + CH 3 COO - partial dissociation H 2 CO 3 = H + + HCO 3 - partial dissociation HCO 3 - = H + + CO 3 2- partial dissociation Weak bases: Those incompletely or partially dissociated into hydroxide (OH - ) and cation Example: NH 3 + H 2 O = NH OH - partial dissociation

Chapter 7. (L26)-Acids and Bases Quiz Time Which of the following is an acidic anhydride? (a) CH 4 ; (b) BF 3 ; (c) H 2 O; (d) SO 3.

Chapter 7. (L26)-Acids and Bases Quiz Time Which of the following is a typical reaction for an acidic anhydride? (a) CH 4 + O 2 = CO 2 + 2H 2 O (b) N 2 + 3H 2 = 2NH 3 ; (c) H 2 O = H + + OH - ; (d) CO 2 + H 2 O = H 2 CO 3

Chapter 7. (L26)-Acids and Bases Quiz Time Which of the following is a basic anhydride? (a) CH 4 ; (b) N 2 ; (c) H 2 O; (d) Li 2 O.

Chapter 7. (L26)-Acids and Bases Quiz Time Which of the following is a typical reaction for a basic anhydride? (a) SO 3 + H 2 O = H 2 SO 4 (b) N 2 + 3H 2 = 2NH 3 ; (c) H 2 O = H + + OH - ; (d) CaO + H 2 O = Ca(OH) 2