Chemistry: Acids and Bases STM Chapter 10 Pages 207-220 Characteristics of Acids and Bases •Chemical opposites •Neutralize one another •Combine in solution to yield water and ‘salt’ (that is, a dissolved ionic compound) Ionic Compound •Chemical substance bound by ionic bonds •Outer electron shells lose and gain electrons –Alkali metals have +1 charge, lose electron –Alkaline earth metals have +2 charge, lose two electrons –Halogens have -1 charge, gain electrons Ionic Bonds •Electrons change elements—ionic bond created •Cations are positive •Anions are negative •Charge amount is important •Valence is amount and character of charge • Acids •Have hydrogen ion in formula (H+) •Taste sour •Dissolve metals Common Acids HCl Hydrochloric acid H2SO4 Sulfuric acid H2CO3 Carbonic acid HNO3 Nitric Acid Bases •Have hydroxide ion in formula (OH-) •Taste bitter •Feel slippery •Also called ‘alkali’, or alkalineCommon Bases NaOH sodium hydroxide, NH3 ammonia •Acids donate proton to base •H+ + OH- → H2O water! •Notice charges add to zero Ions of Acids •H2SO4 : 2H+ + SO42- •HCl : H+ + Cl- •HNO3: H+ + NO3- • H2CO3 : 2H+ + CO32- Metal Oxides are alkaline •Oxide ion of metal compound reacts with water to form two hydroxide ions in water Ions of Bases •Ca(OH)CaO + H2O → Ca(OH)2 2: Ca2+ + 2OH- NaOH: Na+ + OH-• NH3 + H2O → NH4+ + OH- Neutralization Reaction •H+ + OH- → H2O •NaOH + HCl → NaCl + H2O pH •“negative log of hydronium ion concentration in moles per liter” •Pure water has 1x10-7 moles hydronium ions per liter •pH is 7 Neutral p=Power H=hydrogen pH of Acids • More than 1x10-7 hydronium ions per ml •“negative log of hydronium ion concentration” is less than 7 •pH of acids is between 7 and 0pH of Bases • Fewer than 1x10-7 hydronium ions per ml •“negative log of hydronium ion concentration” is more than 7 •pH of bases is between 7 and 14 pH of common solutions: see figure 7.7, p. 215 STM pH Scale •Negative log of the concentration of the Hydronium ion: •Hydrogen donates its proton to water to become H3O+ pH of common solutions Ionic Compounds •Joined by donation/receipt of electrons •Reactions can occur to ‘trade’ ions •Products of reactions have different properties than reactants Reactions •NaCl + AgNO3→? •Na+ + Cl- •Ag+ + NO3- •NaCl + AgNO3→ NaNO3 + AgCl Reactions •NaCl + K2(CrO4)→? •Na+ + Cl- •2K+ + CrO42- •NaCl + K2CrO4→Na2CrO4 + KCl •Not balanced •2 NaCl + K2CrO4→Na2CrO4 + 2KCl Reactions •HCl + CaCO3→ ? → CO2 + some other thingsAre they balanced? •Ca+2H2O→Ca(OH)2+H2 •2LiOH+CO2→Li2CO3+H2O •2Sn+2H2SO4→2SnSO4+SO2+2H2O Are they balanced? •2KNO3+10K→6K2O+N2 •2NH3+O2→N2+3H2O • 3Cl2+6NaOH→ 5NaCl+NaClO3+3H2O Balance these equations •Al+O2→Al2O3 •C3H8+O2→CO2+H2O •Zn(OH)2+H3(PO4)→ Zn3(PO4)2+H2O Molar Mass •SO3 S-32, O-16 •KBrO3 K-39, Br-80 •CaSO4 Ca-40 •Al2(SO4)3
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