ACIDS, BASES, SALTS
U N I T 9
NO T E S
ACIDS
An acid is a substance that produces H+ or H3O+
solution.Properties of acids:1. Sour taste2. React with certain metals to produce hydrogen gas3. React with carbonates and bicarbonates to produce
carbon dioxide gas4. Corrode metals5. React with bases to form a salt and water6. pH is less than 77. Turns blue litmus paper to red “Blue to Red A-CID” 8. Electrolytes- conduct electricity because of ions
RULES FOR NAMING ACIDS#1: ACIDS THAT DO NOT CONTAIN OXYGENHA
Hydrogen/nonmetal
Not in water
1. Hydrogen2. Name of anion
In water
Use prefix “hydro” –root- ic acid
Examples:Formula not in water
in waterHCl hydrogen chloride
hydrochloric acidH2S hydrogen sulfidehydrosulfuric acidHCN hydrogen cyanidehydrocyanic acid
RULES FOR NAMING ACIDS#2: ACIDS THAT CONTAIN OXYGENHAOX
Hydrogen/polyatomic anion
Not in water
1. Hydrogen2. Name of anion
In water
Root name then check ending of anion
-ite
The anion ending changes to –ous acid
-ate
The anion ending changes to –ic acid
EXAMPLES:Formulasalt/gas Formula aqueousHNO2 hydrogen nitrite HNO2 (aq) nitrous acidHNO3 hydrogen nitrate HNO3 (aq) nitric acidH2SO3 hydrogen sulfite H2SO3 (aq) sulfurous
acidH2SO4 hydrogen sulfate H2SO4 (aq) sulfuric acidH2CO3 hydrogen carbonate H2CO3 (aq)
carbonic acid
RULES FOR NAMING ACIDS
PRACTICE PROBLEMS
GIVE THE FORMULA FOR THE NAME OR THE NAME FOR THE FORMULA
H2S H2SO3 (aq) HF (aq)
HClO2 HIO HNO2
H2SO4 (aq) HI (aq) H2C2O4 (aq)
Acetic Acid nitrous acid iodic acid
COMMON ACIDS AND USES
Acid Formula Where found
1. Hydrochloric HCl stomach, cleaning supplies
2. Sulfuric H2SO4 car batteries, fertilizer
3. Nitric HNO3 explosives, fertilizer
4. Phosphoric H3PO4 detergents, fertilizers
5. Carbonic H2CO3 soda (carbonated)
6. Ascorbic H2C2H6O6vitamin C (fruits, vegetables)
7. Acetylsalicylic HOOC-C6H4-OOCCH3 aspirin
8. acetic CH3COOH vinegar
STRONG AND WEAK ACIDS
The most widely used chemical in the world is sulfuric acid.
It can cause severe burns because it is a dehydrating agent.
This means that takes all the water out of materials, including skin.
A strong acid completely ionizes (breaks apart) in water and releases a lot of H+. Example: sulfuric acid (battery acid)
A weak acid only partially breaks down in water, so it doesn’t release much H+. Example: acetic acid (vinegar)
BASES
A base is a substance that produces OH-
solution.Properties of bases:1.Tastes bitter, chalky2.Are electrolytes3.Feel soapy, slippery4.React with acids to form salts and
water5.pH greater than 76.Turns red litmus paper to blue “Basic
Blue”
COMMON BASES AND USES
Base Formula Where found
1. Sodium hydroxide NaOH soap, lye, drain cleaner
2. Potassium hydroxide KOH liquid soap
3. Barium hydroxide Ba(OH)2 stabilizer for plastics
4. Magnesium hydroxide Mg(OH)2 laxative, antacid
5. Calcium hydroxide Ca(OH)2 mortar, plaster, lime
6. Aluminum hydroxide Al(OH)3 deodorant, antacid
7. Ammonia NH3 cleaners, fertilizer, rayon, nylon
STRONG AND WEAK BASES
A strong base completely dissociates (breaks apart) in solution and releases a lot of OH-. Example: sodium hydroxide
A weak base does not completely break apart in solution and does not release as much OH-. Example: aluminum hydroxide
PH
There are many ways to consider acids and bases. One of these is pH.
[H+] is critical in many chemical reactions.A quick method of denoting [H+] is via pH.By definition pH = -log [H+], [H+] = 10-pH
The pH scale, similar to the Richter scale, describes a wide range of values
An earthquake of “6” is 10x as violent as a “5”Thus, the pH scale condenses possible values of [H+] to
a 14 point scaleAlso, it’s easier to say pH = 7 vs. [H+] = 1 x 10-7
PH
The pH scale is a way of expressing the strength of acids and bases
Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the H+ (or OH-) ion.
pH < 7 = acidpH > 7 = basepH = 7 = neutral
PH
Indicators: substance that change color in the presence of acids and bases
Example: bromthymol blue- yellow acid/ blue base/ green neutralphenolthalein- clear acid/ pink base/ light pink neutralphenol red- yellow acid/ pink base/ peach neutralmethyl orange- red acid/ yellow base/ orange neutral
PH CALCULATIONS
Kw = [H+][OH−] = 1 x 10-14
pH + pOH = 14
pH = - log [H+] and pOH = - log [OH-] (The [ ] means Molarity of H+)
Example: If [H+] = 1 x 10-10
pH = - log (1 x 10-10) pH = - (- 10) pH = 10
PH CALCULATIONS
1. If [H+] = 1 X 10-5
pH = - log (1 x 10-5) pH =
2. If the molarity of H+ in a solution is x10 -4, what is the pH?
PH CALCULATIONS
Calculating [H+]
1. If the pH is 2 what is the [H+]10 -pH = [H+][H+] =
2. If the pH is 7 what is the [H+]?
PH CALCULATIONS
Calculating pOHIf [OH-] is 1 x 10 –9
pOH = -log (1 x 10 –9)pOH=
PH CALCULATIONS
Calculating [OH-]1. If the pOH is 3, what is the [OH-]?[OH-] = 10 –pOH
2. If the pH is 8, what is the [OH-]?pOH + pH = or [H+] + [OH-] = 1x10-14
pOH= [OH-] = 10-pOH
NEUTRALIZATION
If you want to neutralize an acid or base, you add a buffer.
Buffers are acids, bases, or salts that are mixed with acids or bases to make their pH closer to 7.
If you want to neutralize an acid, your buffer must be a base.
If you want to neutralize a base, your buffer must be an acid.
Buffers in your body help keep your blood’s pH at 7.4. This is necessary because most of your food contains acids.
NEUTRALIZATION
Neutralization is a chemical reaction between an acid and a base.
H+ from the acid combine with the OH- from the base to form water.
Metals from the base combine with the nonmetals from the acid to form a salt.
Example:HCl + NaOH NaCl + H2O
Most salts are formed with a metal and a nonmetal other than oxygen.
Some salts are formed with a metal and a polyatomic ion.
COMMON SALTS
Salt formula uses
1. Sodium chloride NaCl food preparation
2. Sodium bicarbonate NaHCO3baking soda
3. Calcium carbonate CaCO3 chalk
4. Ammonium chloride NH4Clbatteries
5. Sodium phosphateNa3PO4detergents
ACID RAIN
Unpolluted rain typically has a pH value of 5.6, which is acidic, but not harmful. Any rain that is below 5.6 is considered acid rain.
Acid rain can:1. Dissolve marble in buildings and statues2. Corrode metal (buildings, cars)3. Kill plankton (then fish die)
Ways acid rain can occur:1. Burning coal releases sulfur sulfur combines with water in the air sulfuric acid
forms2. Car exhaust releases nitrogen oxide combines with water nitric acid forms
Ways to prevent acid rain:1. “scrubbers” in smoke stacks2. Nuclear power3. Cleaner fuel
SOAPS, DETERGENTS, AND ESTERS
Soaps are organic salts. This means they contain carbon.
Soaps are made by reacting fats or oils with sodium hydroxide or potassium hydroxide.
Soaps made with NaOH are solids. Soaps made with KOH are liquids. Another product of this reaction is glycerin which is used in lotion.
The process of making soap is called saponification.
SOAPS, DETERGENTS, AND ESTERS
Detergents are similar to soap, but do not form soap scum which is a precipitate that forms when soap is used in hard water (lots of minerals). This is why most laundry products are detergents , not soaps.
An ester is an organic compound formed by the reaction of an organic acid with an alcohol. Esters are responsible for the odors and flavors of flowers, fruits, and other foods. Esters are added to jello and candy to give the flavors of strawberry, banana, or apple.
Organic acids are also used to make polyester fibers.