Acids and Bases

pH Color Chart: Acids and Bases

Acids Sour taste: pH < 7 Turn blue pH paper red Increase H + and H 3 0 concentration of water. Conduct electric current when dissociated (aq). Proton donors. Dangerous when concentrated (  M). Bases Bitter taste: pH > 7 Turn red pH paper blue Increase hydroxide (OH - ) concentration of water. Conduct electric current when dissociated (aq). Proton acceptors. Dangerous when concentrated (M  ). The reaction between an acid and a base creates a salt. Strong Acids and Bases Dissociate Completely in Water.

Acids Due to electronegativity differences, HCl is polar H H Cl HCl (g) H+H+ H+H+ Cl - HCl (aq) δ+ δ-

Hydronium: Coordinate Covalent Bond, The Hydrogen cation attaches itself to a lone pair in a water molecule making H 3 0 H H Cl HCl (g) H+H+ H+H+ Cl - δ+ δ- O HH

Hydronium: Coordinate Covalent Bond, The Hydrogen cation attaches itself to a lone pair in a water molecule making H 3 0 O H H H + A lone hydrogen ion (a PROTON) is much too reactive to stay that way. It quickly attaches itself to water. Protonation: Addition of a proton (H + ) to an atom or molecule.

HCl + H 2 O  H Cl The concentration of Hydronium in water determines its acidity and pH. The more hydronium, the more acidic and the lower its pH.

Why don’t we get H 4 O? O H H H + H

O H H H + H Formal Charge!

Why don’t we get H 4 O? O H H H + H Formal Charge! In hydronium oxygen ends up with a formal charge of +1 but if it formed H 4 O it would have a very unlikely formal charge of plus 2. Formal Charge = #VEs – (#Unshared + #Bonds)

Bases: Sodium hydroxide (NaOH) is an ionic compound. Na + OH - NaOH (s) NaOH (aq) Na + OH -

NaOH(s) + H 2 O(l)  NaOH(aq) The concentration of Hydroxide (OH - ) in water determines the pH of the solution. The more hydroxide, the more basic and the higher its pH. Na + OH -

“Pure” Water has small concentrations of hydronium and hydroxide. 2H 2 0  H 3 O + + OH - H 3 O + + OH -  2H 2 0 FORTUNATELY in very low concentrations that equalize. (2ppb) Water has a pH of 7 (neutral) but tap water might be slightly basic..

What type of solutions would these be? Na + OH - NaOH (aq) HCl (aq) H+H+ H+H+ Cl -

What type of solutions would these be? Na + OH - NaOH (aq) HCl (aq) H+H+ H+H+ Cl - Base pH > 7 Acid pH < 7

H+ ion attaches to water forming Hydronium (H 3 O) Na + OH - NaOH (aq) HCl (aq) H3O+H3O+ H3O+H3O+ Cl - Base pH > 7 Acid pH < 7

What happens when we mix an acid and a base? Na + OH - NaOH (aq) HCl (aq) H3O+H3O+ H3O+H3O+ Cl - Base pH > 7 Acid pH < 7

What happens when we mix an acid and a base? Na + OH - NaOH (aq) + HCl (aq)  ??? H3O+H3O+ H3O+H3O+ Cl -

What happens when we mix an acid and a base? Na + OH - NaOH (aq) + HCl (aq)  ??? H3O+H3O+ H3O+H3O+ Cl -

Acid-Base Neutralization! Na + OH - NaOH (aq) + HCl (aq)  2H 2 0 H3O+H3O+ H3O+H3O+ Cl - The Hydroxide and Hydronium combine to form WATER neutralizing one another… pH = 7!!!

Acid-Base Neutralization! Na + H2OH2O H2OH2O NaOH (aq) + HCl (aq)  2H NaCl (aq) Cl - WE ARE LEFT WITH NaCl(aq) WHICH IS SALT WATER! H2OH2O H2OH2O

Making Salt! So we can go into the lab and mix 1M solutions of NaOH and HCl and evaporate away the water leaving behind salt. We will use an indicator to make sure we have even amounts of both ( where pH = 7!) and expose a cool color changing trick as simple chemistry. So we can go into the lab and mix 1M solutions of NaOH and HCl and evaporate away the water leaving behind salt. We will use an indicator to make sure we have even amounts of both ( where pH = 7!) and expose a cool color changing trick as simple chemistry.

Sulfuric Acid and Sodium Oxide H 2 SO 4(aq)  2H + (aq) + S (aq) + 2H 2 O  2H 3 0 (aq) + SO 4 2- (aq) Na 2 O (aq)  2Na + (aq) + O 2- (aq) + H 2 O  2OH - (aq) + 2Na + (aq) 2OH - (aq) + 2Na (aq) + 2H 3 0 (aq) + SO 4 2- (aq)  4H Na 2 SO 4(s) Sulfuric Acid and Sodium oxide yield water and Sodium Sulfate (Salt). Simplified: H 2 SO 4 + Na 2 O  4H Na 2 SO 4

Assignment What is an acid? What is a base? Details! Some fruits taste sour, why? What is their pH? What is a Tums made of? How does it work? Draw the Lewis structure for Hydronium. Combining an acid and a base produces what? Research and find a neutralization reaction for another acid and base that produces a salt. Break the equation down and explain it step by step. Why is it a bad idea to mix drain cleaner with other chemicals? What is the natural pH of rain water? Explain why it has the pH that it does and include the chemical reactions taking place. Explain what man-made acid rain is, what does it form from, how is it produced, effects on the environment? Is it preventable? Why does blowing air into a solution with an indicator make it change color? What is happening? A solution has a pH of 10, acid or base? Explain the “water to wine” and back trick. Explain the punny picture: Create a lemon battery that powers an LED light… Explain how it works. What kind of acid is in a car battery? In your stomach?