11

Acids and Acids and BasesBases Acids and Acids and BasesBases

22

• Acids and bases are encountered frequently both in chemistry and in everyday living. They have opposite properties and have the ability to cancel or neutralize each other. Acids and bases are carefully regulated in the body by the lungs, blood, and kidneys through equilibrium processes.

33

• Vinegar contains acetic acid, which makes it taste sour. 

•Onions release a gas which turns into sulfuric acid when it reaches your eyes, making them burn. 

44

•   Soap, baking soda, milk of magnesia, and ammonia all contain bases.  These substances exhibit some of the physical properties of bases, such as feeling slippery, tasting bitter, and dissolving greases.  Bases also irritate the skin and eyes just as acids do. 

55

66

77

88Some Properties of Acids

1. Arhenius Theory: Acids produce H+ ions in water:

HCl => H+ + Cl-

2. Taste sour

3. Corrode metals

4. Conduct electricity: Electrolytes

5. React with bases to form a salt and water

HCl + NaOH => NaCl + H2O

6. pH is less than 7

7. Change color of indicators

99

Common Acids

• Acetic acid (CH 3 COOH): vinegar

• Acetylsalicylic acid (HOOCC 6 H 4 OOCCH 3 ): aspirin

• Ascorbic acid (H 2 C 6 H 6 O 6 ): vitamin C

• Carbonic acid (H 2 CO 3 ): soft drinks, seltzer water

• Citric acid (C 6 H 8 O 7 ): citrus fruits, artificial flavorings

• Hydrochloric acid (HCl): stomach acid

• Nitric acid (HNO 3 ): fertilizer, explosives

• Sulfuric acid (H 2 SO 4 ): car batteries

1010Common Bases

• Aluminum hydroxide (Al[OH] 3 ): antacids, deodorants

• Ammonium hydroxide (NH 4 OH): glass cleaner

• Magnesium hydroxide (Mg[OH] 2 ): laxatives, antacids

• Sodium bicarbonate/sodium hydrogen carbonate (NaHCO 3 ): baking soda

• Sodium carbonate (Na 2 CO 3 ): dish detergent

• Sodium hydroxide (NaOH): lye, oven and drain cleaner

• Sodium hypochlorite (NaClO): bleach

1111

Acids have a

pH less than 7

1212

12

The pH Scale

1313

Naming Acids

h yd ro - p re fix-ic en d in g

2 e lem en ts

-a te en d in gb ecom es-ic en d in g

-ite en d in gb ecom es

-o u s en d in g

n o h yd ro - p re fix

3 e lem en ts

AC ID Ss ta rt w ith 'H '

1414

http://www.chemistry.wustl.edu/~courses/genchem/Tutorials/Naming/Acids.htm

Anion name Acid name

hypo___ite hypo___ous acid

___ite ___ous acid

___ate ___ic acid

per___ate per___ic acid

1515

Name of Anion Name of Acid Examples

.....-ide Hydro.....-ic acid HBr bromide → hydrobromic acid

Per .....-ate Per .....-ic acid HClO4 perchlorate → perchloric acid

.....-ate .....-ic acid HClO3 chlorate → chloric acidH2SO4 sulfate → sulfuric acid

.....-ite .....-ous acid HClO2 chlorite → chlorous acidH2SO3 sulfite → sulfurous acid

Hypo...-ite Hypo....-ous acid HClO hypochlorite → hypochlorous acid

1616

• HBr HBr (aq)(aq)

• HH22COCO33

• HH22SOSO33

• HH22SOSO44

hydrohydrobromicbromic acidacid

carboncarbonicic acidacid

sulfursulfurousous acidacid

Acid Nomenclature Review

SulfurSulfuric ic acidacid

1717

Some Properties of Bases

Produce OHProduce OH-- ions in water: ions in water:

NaOH => NaNaOH => Na+1 +1 + OH + OH-1 -1

Taste bitter, chalkyTaste bitter, chalky

Are electrolytesAre electrolytes

Feel soapy, slipperyFeel soapy, slippery

React with acids to form salts and waterReact with acids to form salts and water

pH greater than 7pH greater than 7

Change color of indicatorsChange color of indicators

1818

Common Bases

NaOHNaOH sodium hydroxidesodium hydroxide lyelye

KOHKOH potassium hydroxidepotassium hydroxide liquid soapliquid soap

Ba(OH)Ba(OH)22 barium hydroxidebarium hydroxide stabilizer for plasticsstabilizer for plastics

Mg(OH)Mg(OH)22 magnesium hydroxidemagnesium hydroxide “MOM” Milk of magnesia“MOM” Milk of magnesia

Al(OH)Al(OH)33 aluminum hydroxidealuminum hydroxide Maalox (antacid)Maalox (antacid)

1919

Acid/Base definition

Arrhenius (traditional)

Acids – produce H+ ions in aqueous solution

Bases – produce OH- ions in aqueous solution

2020

Concentration of a Solution

• An aqueous solution consists of at least two components, the solvent (water) and the solute (the stuff dissolved in the water).

• Usually one wants to keep track of the amount of the solute dissolved in the solution. We call this the concentration.

2121

The The pH scalepH scale is a way of is a way of expressing the strength of expressing the strength of acids and bases.acids and bases.

Instead of using very Instead of using very small numbers, we just use small numbers, we just use the NEGATIVE power of 10 the NEGATIVE power of 10 on the Molarity of the acid.on the Molarity of the acid.

pH = - log [acid]

2222Concentration , MConcentration , MConcentration , MConcentration , M

The amount of solute in a solution is given The amount of solute in a solution is given by its by its concentrationconcentration, or molarity, or molarity

M = n / V and n = m / MMM = n / V and n = m / MM

Molarity (M) = moles soluteliters of solution

2323

2.A basic solution was made by 2.A basic solution was made by dissolving 15g of cadmium III dissolving 15g of cadmium III hydroxide in 390 mL of water. What is hydroxide in 390 mL of water. What is the pH?the pH?

2424

pH = -log [H+] [ H+ ] = 10-pH

pOH = -log [OH-] [ OH- ] = 10-pOH

pH + pOH = 14

[H] [OH] = 1 x 10 -14

pH Formulas

2525Calculating the pH

pH = - log [H+] (Remember that the [ ] means Molarity)

For HCl , [ H+ ] = [HCl]

For H2 SO4 , [ H+ ] = 2 x [H2SO4]

2626

Try These!Try These!

Find the pH of these:Find the pH of these:

1)1) A 0.15 M solution of Hydrochloric acid.A 0.15 M solution of Hydrochloric acid.

2) A 3.00 X 102) A 3.00 X 10-7-7 M solution of Sulfuric Acid. M solution of Sulfuric Acid.

3) A 1.2 x 103) A 1.2 x 10-4-4 M solution of Aluminum M solution of Aluminum hydroxidehydroxide

2727pH calculations – Solving for pH calculations – Solving for H+H+pH calculations – Solving for pH calculations – Solving for H+H+

If the pH of Coke is 3.12,If the pH of Coke is 3.12,

What is [HWhat is [H++] = ???] = ???

2828pH calculations – Solving for pH calculations – Solving for H+H+

• A solution has a pH of 8.5. What is the A solution has a pH of 8.5. What is the Molarity of hydrogen ions in the Molarity of hydrogen ions in the solution?solution?

2929

[H[H33OO++], [OH], [OH--] and pH] and pHWhat is the pH of the What is the pH of the

0.0010 M NaOH solution? 0.0010 M NaOH solution?

3030The pH of rainwater collected in a certain region of the northeastern United States on a particular day was 4.82. What is the H+ ion concentration of the rainwater?

The OH- ion concentration of a blood sample is 2.5 x 10-7 M. What is the pH of the blood?

3131

[OH[OH--]]

[H[H++]] pOHpOH

pHpH

1010 -pOH

-pOH

1010 -pH-pH-Log[H

-Log[H++]]

-Log[OH

Log[OH

--]]

14 -

pOH

14 -

pOH

14 -

pH

14 -

pH

1.0

x 10

1.0

x 10-1

4-14

[OH[O

H-- ]]

1.0

x 10

1.0

x 10-1

4-14

[H[H

++ ]]

3232Calculating [H3O+], pH, [OH-], and pOH

Problem 1: A chemist dilutes concentrated hydrochloric acid to make two solutions: (a) 3.0 M and (b) 0.0024 M. Calculate the [H3O+], pH, [OH-], and pOH of the two solutions at 25°C.

Problem 2: What is the [H3O+], [OH-], and pOH of a solution with pH = 3.67? Is this an acid, base, or neutral?

Problem 3: Problem #2 with pH = 8.05?

3333pH testing

• There are several ways to test pHThere are several ways to test pH

–Blue litmus paper (red = acid)Blue litmus paper (red = acid)

–Red litmus paper (blue = basic)Red litmus paper (blue = basic)

–pH paper (multi-colored)pH paper (multi-colored)

–pH meter (7 is neutral, <7 acid, >7 base)pH meter (7 is neutral, <7 acid, >7 base)

– Indicators like phenolphthaleinIndicators like phenolphthalein

–Natural indicators like red cabbageNatural indicators like red cabbage

3434pH indicators

• Indicators are dyes that will change color in the presence of an acid or base

• Some indicators only work in a specific range of pH

• Some dyes are natural, like red cabbage.

• http://dept.sfcollege.edu/natsci/chem/indtbl.htm

3535LAB: Red Cabbage , Bromothymol Blue or pH

paper ???

3636

Phenophtalein & Bromothymol Blue

3737

Sample Red Cabbage pH

Bromothymol Blue

pH paper Acidic orBasic

1. Milk

2.Orange Juice

3838

pH meter

• Tests the voltage of the Tests the voltage of the electrolyteelectrolyte

• Converts the voltage to Converts the voltage to pHpH

• Very cheap, accurateVery cheap, accurate

• Must be calibrated with Must be calibrated with a buffer solutiona buffer solution