Introduction to ACIDS and BASES

What are Acids and Bases? Warm Up Title your CB- What are Acids and Bases? Write everything you know about the properties of acids and bases. 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 Bases 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. Shampoo Lemonade Windex 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)

What is happening in the tube? Rainbow Tube Demo What is happening in the tube?

WATER Water molecules are highly polar and are in continuous motion when at room temperature. When collisions between water molecules occur, a hydrogen ion can transfer from one water molecule to another. This is called the self-ionization of water.

Self Ionization of Water Water 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:

Where X are the coefficients in the 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

4/19 Warm Up- Look through Acid/Base Notes! What are the properties of acids? What are properties of bases? We know that there was some crazy equilibrium crap (did I just say that?)… We also know that there is a relationship between [H+] and [OH-] ions. Last-- we know that there is a pH scale. Hmmmmmm……. How does it all fit together?

Lets start with the pH scale pH is a logarithmic function based on the [H+]

KW = [H+] [OH-] = 1.0 X 10-14 (mol/L)2 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!! [H+]= 1.0 x 10-7 [H+]= 1.0 x 10-5 [H+]= 1.0 x 10-9 [H+]= 2.5 x 10-9 [H+]= 1.6 x 10-5 [H+]= 3.7 x 10-9

How did you do? [H+]= 1.0 x 10-7 pH= 7 [H+]= 1.0 x 10-5 pH= 5 [H+]= 1.0 x 10-9 pH= 9 [H+]= 2.5 x 10-9 pH= 8.6 [H+]= 1.6 x 10-5 pH= 4.8 [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 Columns 7-8 are the calculations we learned on Friday. 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

NaOH  Na+ (aq) + OH- (aq) 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 Explain that pH scale is an exponential model.

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.