introduction to acids and bases warm up 1.title your cb- what are acids and bases? 2.write...
TRANSCRIPT
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.