Acids and Bases Lesson 1 Acid & Base Properties (Strong & Weak acids)

Taste bitter (baking soda) Change litmus paper blue Feel slippery Are electrolytes that conduct electricity Neutralize acids Properties of Bases Ex: NaOH, Ca(OH) 2, KOH, Zn(OH) 2 -- notice they all contain OH.

Taste sour (vinegar, lemon juice) Change litmus paper red React with metals such as Mg and Zn to make H 2 Mg(s)+ 2 HCl (aq)  MgCl 2 (aq) + H 2(g). Are electrolytes that conduct electricity Neutralize bases Properties of Acids Ex: HCl, HNO 3, H 2 SO 4 –notice they all contain H.

Salts A salt is the neutralization product when an acid and a base react to produce water. HCl + NaOH  NaCl + H 2 O Notice, a salt does not contain H, or OH.

The Arrhenius Theory of Acids and Bases

Arrhenius acid HCl  Arrhenius base NaOH  Na + + OH - H + + Cl - produces H + in solution produces OH - in solution H + is called a proton

Bronsted-Lowry Theory of Acids and Bases

-more general theory -to accommodate reactions at equilibrium. -acids as proton donors -bases as proton acceptors

H+H+ Bronsted Acid H+H+ HCl + H 2 O  Bronsted Base NH 3 + H 2 O ⇄ A proton donor A proton acceptor Chemistry 12 H 3 O + + Cl - NH OH - weak strong

H+H+ H+H+ Write a Bronsted reaction for the base HCO 3 - base acid base HCO 3 - ⇄ H 2 CO 3 + OH - + H 2 O weak These are called “Conjugate acid-base pairs” They differ by one proton H + HCO 3 - and H 2 CO 3 H 2 O and OH -

5. H + is the same as H 3 O + 4. Bronsted acids donate a proton to water to form H 3 O + 3. Arrhenius acids dissociate in water to form H + 2. Bronsted bases accept a proton from water to produce OH - 1. Arrhenius bases dissociate in water to produce OH - In Summary

H + is another way to show H 3 O +. Hydronium ion H3O+H3O+ H + + H 2 O ⇋ + H+H+ H2OH2O Proton

Conjugate acids and bases

Conjugates A conjugate acid-base pair (conjugate pair) is a pair of chemical species which differ by only one proton (H+) NH 4 +, NH 3 A conjugate acid is the member of conjugate pair that HAS the extra proton. NH 4 + A conjugate base is the member of the conjugate pair that LACKS the extra proton. NH 3

NH 4 + NH 3 Fe(H 2 O) 6 3+ OH - HCO 3 - HPO 4 2- PO 4 3- HPO 4 2- H 2 PO 4 - H 2 CO 3 H2OH2O One more H + 1 less H + Conjugate BaseConjugate Acid C 6 H 5 COOHC 6 H 5 COO - C 6 H 5 OHC6H5O-C6H5O- Fe(H 2 O) 5 (OH) 2+ H+ gives a +1 Charge.

Acids and Bases Chart p334 Relative Strengths of Bronsted-Lowry Acids and Bases Aqueous solutions at room temperature.

Strong Acids Weak Acids

HCl + H 2 O  H 3 O + + Cl - Use a “  ” and not “ ⇄ ” because it is not an equilibrium situation. Have very large Ka’s, that is why you do not find them on the chart. Produce large amounts of H 3 O +. Are good conductors. Completely ionize in water Left side of Acid Chart -top six- Strong Acids

Weak Acids Left side of the Acid Chart below the top six. Do not completely ionize in water. Are poor conductors. Produce small amounts of H 3 O +. Have small Ka’s, you will find Ka values on the chart. Use a “ ⇄ ” and not “  ” It means they are Equilibrium situations! HF + H 2 O ⇄ H 3 O + + F - Ka=[H 3 O + ][F - ] =3.5 x from page 334 [HF] Water is not included because it is a pure liquid! Its concentration is constant !

You can also write: HF + H 2 O ⇄ H 3 O + + F - HF + H 2 O ⇌ H + + F - [H + ][F - ] Ka = =3.5 x [HF] We use H + and H 3 O + interchangeably. They mean the same thing!

Balance these neutralization equations H 2 SO 4 + NaOH HCl + Sn(OH) 4

Homework: Hebden: Pg 110 #1-2, Pg. 112 #3-4