Introduction toACIDS and BASES

Warm Up

1. Title your CB-

What are Acids and Bases?

2. Write everything you know about the properties of acids and bases.

3. Why are they important?

Acids and Bases are part of your everyday lives!

Acids Bases

Definition

An acid is a compound that produces hydrogen ions (H+) when dissolved in water.

A base is a compound that produces hydroxide ions (OH-) when dissolved in water.

Properties of Acids and BasesAcids

• Sour taste• Neutralize bases• Release hydrogen

gas when added to an active metal

• Aqueous solutions of acids are electrolytes (conduct electricity)

Bases• Bitter taste• Feels slippery• Neutralize acids• Aqueous solutions

of bases are electrolytes (conduct electricity)

What do you think?

1. Based on the properties of the following, predict if the product is an acid or base.

a. Shampoo

b. Lemonade

c. Windex

d. Gatorade

2. Do you think Draino is an acid or a base? Why?

Warm Up

Things I am collecting:

Article Analysis

Chapt 12.1 Notes

Molarity Packet

Review

Things I have already collected:

KNO3 Lab

Solubility Rule Lab

Solubility Curve WS (not the one with water)

Rainbow Tube Demo

What is happening in the tube?

WATER

Self Ionization of WaterWater molecules collide with one another to

cause the self-ionization reaction represented by this equation:

2H2O H3O+ + OH-

It is a reversible reaction so the equation is usually written with the arrows going in both directions:

2H2O H3O+ + OH-

Self Ionization of Water

In pure water the H+ and OH- are produced in a 1:1 ratio.

[H+] = [OH-]

A neutral solution is when [H+] = [OH-]

Water is a Neutral Solution!

Self Ionization of Water

In any aqueous solution [H+] and [OH-] are interdependent.

[H+] increases then [OH-] decreases.

[H+] decreases then [OH-] increases.

This is an example of Le Chatelier’s Principle.

Le Chatelier’s Principle

Equilibrium

H2O H+ + OH-

If a stress is applied to a system in a dynamic equilibrium, the system changes to relieve the stress.

Le Chatelier’s Principle

If we add more reactants the system looks like this:

However, the system will correct itself and make more products to balance the system.

Le Chatelier’s Principle

Similarly, if we add more products to the system, it will look like this:

But a system that is in equilibrium will shift again to relieve stress:

Equilibrium Constant

For every reaction there is a mathematical relationship between the reactants and products.

Keq = [Products]x

[Reactants]x

Where X are the coefficients in the balanced equation.

Example

Write the equilibrium constant for the following reaction.

H2SO4 + 2NaOH Na2SO4 + 2HOH

Lets start with the pH scale

pH is a logarithmic function based on the [H+]

The first step in pulling it all together is knowing the

Ion-Product Constant for Water KW

The product of the concentrations of the hydrogen ions and hydroxide ions in water is KW and equals 1.0 X 10-14 (mol/L)2

KW = [H+] [OH-] = 1.0 X 10-14 (mol/L)2

[H+] = 1.0 X 10-7 mol/L [OH-] = 1.0 X 10-7 mol/L

Knowing Kw and the concentration of one of the variables, we can determine the other!

Go to the WS

Calculating pH

Keeping in mind that pH is a logarithmic function, we can calculate the pH using the following equation.

pH = -log [H+]

Try these! Determine the pH.Get your calculators out!!

1. [H+]= 1.0 x 10-7

2. [H+]= 1.0 x 10-5

3. [H+]= 1.0 x 10-9

4. [H+]= 2.5 x 10-9

5. [H+]= 1.6 x 10-5

6. [H+]= 3.7 x 10-9

How did you do?

1. [H+]= 1.0 x 10-7 pH= 72. [H+]= 1.0 x 10-5 pH= 53. [H+]= 1.0 x 10-9 pH= 94. [H+]= 2.5 x 10-9 pH= 8.65. [H+]= 1.6 x 10-5 pH= 4.86. [H+]= 3.7 x 10-9 pH= 8.4

What is pOH

pOH is a logarithmic function of the [OH-].

It works exactly the same as pH.

pOH = -log[OH-]

What is the relationship between pH and pOH??

pH + pOH = 14

Yea!

Calculations

5. Columns 7-8 are the calculations we learned on Friday.

6. Columns 9 and 10- Concentration is in mol/L. Calculate how many moles in 2L of solution.

Adding Acid to Water

HCl H+ (aq) + Cl- (aq)

The acid adds more H+ increasing the [H+] in the water. Therefore in any acid solution the [H+] will be greater than the [OH-].

[H+] > 1.0 X 10 -7 mol/L

[H+] > 0.0000001 mol/L

Adding Base to Water

NaOH Na+ (aq) + OH- (aq)

The base adds more OH- increasing the [OH-] in the water. Therefore in any basic solution the [OH-] will be greater than the [H+].

[H+] < 1.0 X 10 -7 mol/L[H+] < 0.0000001 mol/L

pH Scale

The pH of a solution is the negative logarithm of the hydrogen-ion concentration.

pH = -log [H+]

Neutral pH = 7 [H+] = 1.0 X 10 -7 mol/L

Acidic pH < 7 [H+] > 1.0 X 10 -7 mol/L

Basic pH > 7 [H+] < 1.0 X 10 -7 mol/L

pH Scale

Indicator

A substance that “indicates” the pH of a solution by changing color.

Red Litmus Paper

Blue Litmus Paper

Universal Indicator Paper

Red Cabbage Juice

Household pH Lab

You will be testing the pH of many solutions that you use every day.

1. What do you think?

2. Cabbage Juice- 10 mL juice, add a few drops of sample.

2. Litmus Paper– Use blue and red!

(example: Red turns Blue)

3. Universal pH paper- record color and approximate pH.

4. Actual pH- from meter (I will give you these).

Arrhenius Definition

An acid is a compound that produces hydrogen ions (H+) when dissolved in water.

A base is a compound that produces hydroxide ions (OH-) when dissolved in water.