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.