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Acids and Bases

Acids and Bases. Objectives: 1. Distinguish between strong and weak acids; identify the seven common strong acids. 2. Distinguish between strong and weak bases; identify the common strong bases. 3. Write a net ionic equation for any type of acid-base reaction.

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Acids and Bases

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  1. Acids and Bases Objectives: 1. Distinguish between strong and weak acids; identify the seven common strong acids. 2. Distinguish between strong and weak bases; identify the common strong bases. 3. Write a net ionic equation for any type of acid-base reaction. 4. Given the equation for an acid-base reaction, select the Bronsted acid and Bronsted base; 5. Identify the Lewis acid and Lewis base; conjugate acid-base pairs.

  2. + - I. Arrhenius definition of Acids and Bases Base: forms OH- in solution Strong base is completely dissociated in water: Ca(OH)2(s)  Ca2+(aq) + 2 OH-(aq) Weak base is partially dissociated to form OH - ions. NH3(g) + H2O NH4+(aq) + OH- • Acid: forms H3O+ ion in water • Strong acids are completely dissociated in water: • HCl(aq)  H+(aq) + Cl-(aq) • Weak acids are partially dissociated in water • HF(aq) H+(aq) + F-(aq) 7 STRONG ACIDS HCl, HBr, HI, HNO3, HClO4, HClO3, H2SO4 STRONG BASES LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2

  3. II. Bronsted-Lowry definition • An acid is a protondonor ; • A base is a proton acceptor • HF(aq) + OH-(aq) <==> F- (aq) + H2O • acid base conj. base conj. acid • NH3(aq) + H2O <===> NH4+(aq) + OH-(aq) • base acid conj. acid conj. base • HCl(aq) + H2O <====> H3O+(aq) + Cl-(aq) • acid base conj. acid conj. base • H3O+ is referred to as the conjugate acid of H2O • OH- is the conjugate base of H2O *Note that water can act as either an acid or a base in the Bronsted-Lowry definition!

  4. III> Lewis Definition • . Acid accepts (AA) electron pair donated by base. • H+(aq) + H2O : H3O+(aq) • acidbase • Zn2+ (aq) + 4H2O : Zn(H2O)42+ (aq) • acidbase • a Lewis base has unshared pair of electrons molecules from groups 5, 6, or 7 • a Lewis base donates it’s pair of electrons to • H+ions • metallic cations • Amino Acids ‘ Carboxyl group’ are Lewis acids • Amino Acids ‘ Amine group’ are Lewis bases • Metal ions are Lewis Acids.

  5. I. Arrhenius Acids form H3O+, Bases form OH- HCl H3O + + Cl- Ca(OH)2 Ca2+ + 2 OH- • Bronsted-Lowry • Acids donate protons Bases accept protons • HF + OH- F- + H2ONH3 + H2O  NH4+ + OH- • Lewis • Acids are electron pair Bases are electron pair • acceptors donors • Zn2+ (aq) + 4H2O : Zn(H2O)42+ (aq • acidbase

  6. pH Calculations memorize these equations pOH + pH = 14.00 pOH = - log10 [OH-] [OH-] = 10-pOH . pH = - log10[H+] [H+] = 10 -pH K water = [H+][OH-] = 10-14

  7. The pH scale pH [H3O+] [OH-] example 14 1x10-14 1x10-0 13 1x10-13 1x10-1NaOH 12 1x10-12 1x10-2 ammonia 10 1x10-10 1x10-4milk of magnesia 7 1 x 10-7 1 x 10-7 1x10-7 1x10-7 water, blood 3 1x10-3 1x10-11cola, vinegar 2 1x10-2 1x10-12 lemon juice 1 1 x 10-1 1 x 10-13 gastric juice basic neutral acidic

  8. *Writing Net Ionic Acid-Base Reactions: 1. SA + SB: (H+ + Cl- + Ca+2 + 2(OH -) ) net: H+(aq) + OH-(aq)  H2O neutral pH at equivalence. 2. SB + weak acid (HF + Ca+2 + 2(OH -)) net: HF(aq) + OH- H2O + F-(aq) ph is > 7 at equivalence. 3. SA + weak base (H+ + Cl-+ NH3 ) net: H+(aq) + NH3(aq)  NH4+(aq) ph is < 7 at equivalence. *Weak or insoluble -- written as molecular strong or soluble -- written as ions. Do not include spectator ions!! *Notice that weak acids form basic solutions, and weak bases form acidic solutions. ***What happens when there is a limiting reactant in each of the above reactions?

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