Acids and Bases

pH Color Chart: Acids and Bases

pH Color Chart: Acids and Bases

Acids• Sour taste: pH < 7• Turn blue pH paper red• Increase H+ and H30

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 Cl HCl(g) Disassociation

H+

Cl -

HCl(aq)

δ+ δ-

Hydronium: Coordinate Covalent Bond, The Hydrogen cation attaches itself to a lone pair in a water molecule making H30

H Cl HCl(g)

H+

Cl -

δ+ δ-

OHH

Hydronium: Coordinate Covalent Bond, The Hydrogen cation attaches itself to a lone pair in a water molecule making H30

O HH

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 + H2O H30 + 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 H4O?

O HH

H +

H

Why don’t we get H4O?

O HH

H +

H

Formal Charge!

Why don’t we get H4O?

O HH

H +

H

Formal Charge!In hydronium oxygen ends up with a formal charge of +1 but if it formed H4O 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)

Dissociation

NaOH(aq)

Na+

OH-

NaOH(s) + H2O(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.

• 2H20 H3O+ + OH-

• H3O+ + OH- 2H20

• 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)

Dissociation

HCl(aq)

H+

Cl-

What type of solutions would these be?

Na+

OH-

NaOH(aq)

Dissociation

HCl(aq)

H+

Cl-

Base pH > 7Acid pH < 7

H+ ion attaches to water forming Hydronium (H3O)

Na+

OH-

NaOH(aq) HCl(aq)

H3O+

Cl-

Base pH > 7Acid pH < 7

What happens when we mix an acid and a base?

Na+

OH-

NaOH(aq) HCl(aq)

H3O+

Cl-

Base pH > 7Acid pH < 7

What happens when we mix an acid and a base?

Na+

OH-

NaOH(aq) + HCl(aq) ???

H3O+

Cl-

What happens when we mix an acid and a base?

Na+

OH-

NaOH(aq) + HCl(aq) ???

H3O+

Cl-

Acid-Base Neutralization!

Na+

OH-

NaOH(aq) + HCl(aq) 2H20

H3O+

Cl-

The Hydroxide and Hydronium combine to form WATER neutralizing one another… pH = 7!!!

Acid-Base Neutralization!

Na+

H2O

NaOH(aq) + HCl(aq) 2H20 + NaCl(aq)

Cl-

WE ARE LEFT WITH NaCl(aq) WHICH IS SALT WATER!

H2O

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.

Sulfuric Acid and Sodium Oxide

H2SO4(aq) 2H+(aq) + S04

2-(aq) + 2H2O 2H30(aq) + SO4

2- (aq)

Na2O(aq) 2Na+(aq) + O2-

(aq) + H2O 2OH-

(aq) + 2Na+

(aq)

2OH-(aq)

+ 2Na(aq) + 2H30(aq) + SO42-

(aq) 4H20 + Na2SO4(s)

Sulfuric Acid and Sodium oxide yield water and Sodium Sulfate (Salt).

Simplified: H2SO4 + Na2O 4H20 + Na2SO4

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?