•pH less than 7•Neutralizes bases(form salts and

water)•Forms H + (H3O+) ions in solution•Corrosive-reacts with most metals•Good conductors of electricity•Taste sour

HNO3 + H2O H3O+ + NO3

Weak Acids do not ionize completely: Acetic, Boric, Nitrous, Phosphoric, Sulfurous

Strong Acids ionize completely: Hydrochloric, Nitric; Sulfuric, Hydriodic

• HCl- hydrochloric- stomach acid

• H2SO4- sulfuric acid - car batteries

• HNO3 – nitric acid - explosives

• HC2H3O2- acetic acid - vinegar

• H2CO3-carbonic acid – sodas

• H3PO4- phosphoric acid -flavorings

pH greater than 7Feels slippery, soapyTaste bitter, chalkyAre electrolytesDissolves fats and oilsUsually forms OH- ions in solution

Neutralizes acids

Weak Bases: ammonia; potassium carbonate, sodium carbonate

Strong Bases: sodium hydroxide; sodium phosphate; barium hydroxide; calcium hydroxide

NaOH- sodium hydroxide (LYE) soaps, drain cleaner

Mg (OH)2 - magnesium hydroxide-antacids Al(OH)3-aluminum hydroxide-antacids,

deodorants NH4OH-ammonium hydroxide- “ammonia”

LecturePLUS Timberlake 9

Describe the solution in each of the following as: 1) acid 2) base or 3)neutral.A. ___soda

B. ___soapC. ___coffeeD. ___ wineE. ___ water

F. ___ grapefruit

LecturePLUS Timberlake 10

Describe each solution as: 1) acid 2) base or 3) neutral.A. _1_ soda

B. _2_ soapC. _1_ coffeeD. _1_ wineE. _3_ water

F. _1_ grapefruit

LecturePLUS Timberlake 11

Identify each as characteristic of an A) acid or B) base____ 1. Sour taste ____ 2. Produces OH- in aqueous solutions

____ 3. Chalky taste____ 4. Is an electrolyte____ 5. Produces H+ in aqueous solutions

LecturePLUS Timberlake 12

Identify each as a characteristic of an A) acid or B) base

_A_ 1. Sour taste

_B_ 2. Produces OH- in aqueous

solutions

_B_ 3. Chalky taste

A, B 4. Is an electrolyte

_A_ 5. Produces H+ in aqueous solutions

We use this scale to measure the strength of an acid or base.

pH is defined as the –log[H+] pH can use the concentration of hydronium

ions or hydrogen ions.

14

• Most living cells have a very narrow range of tolerance for pH, i.e. [H+].

• The [H+] concentration will be important (either explicitly or implicitly) for many other topics in biology.

• [H+] is controlled in all biological organisms, and in virtually all biochemical experiments.

• Each pH unit represents a factor of 10 difference in [H+].

The pH scale goes from 0 to 14—because [H[H++][OH][OH--] = 10] = 10-14-14

pH

10-2

10-3

10-5

10-4

10-8

10-7

10-6

[H+] M

10-10

10-9

10-11

10-12

10-13

10-14

10-1

100 A strong acid

A strong base

SOURCE: http://en.wikipedia.org/wiki/Image:PH_scale.png#file

14 1 x 10-14 1 x 10-0 0 13 1 x 10-13 1 x 10-1 1 12 1 x 10-12 1 x 10-2 2 11 1 x 10-11 1 x 10-3 3 10 1 x 10-10 1 x 10-4 4 9 1 x 10-9 1 x 10-5 5 8 1 x 10-8 1 x 10-6 6

6 1 x 10-6 1 x 10-8 8 5 1 x 10-5 1 x 10-9 9 4 1 x 10-4 1 x 10-10 10 3 1 x 10-3 1 x 10-11 11 2 1 x 10-2 1 x 10-12 12 1 1 x 10-1 1 x 10-13 13 0 1 x 100 1 x 10-14 14

NaOH, 0.1 MHousehold bleachHousehold ammonia

Lime waterMilk of magnesia

Borax

Baking sodaEgg white, seawaterHuman blood, tearsMilkSalivaRain

Black coffeeBananaTomatoesWineCola, vinegarLemon juice

Gastric juice

Mor

e ba

sic

Mor

e ac

idic

pH [H1+] [OH1-] pOH

7 1 x 10-7 1 x 10-7 7

pH = 3

pH = 7

pH = 11

OH-

H3O+OH-

OH-H3O+

H3O+

[H3O+] = [OH-] [H3O+] > [OH-] [H3O+] < [OH-]

acidicsolution

neutralsolution

basicsolution

con

cen

trat

ion

(m

oles

/L)

10-14

10-7

10-1

Timberlake, Chemistry 7th Edition, page 332

pH = -log [H+]

Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 285

Indicator Acid color

Neutral color

Base color

Phenolphthalein Colorless Faint pink Dark pink

Bromthymol blue

Yellow Green Blue

Litmus Red ----- Blue

pH paper changes color to indicate a specific pH value.

A buffer is a solution that resists changes in pH when small amounts of acids and bases are added.

“Heartburn” Planting vegetables and flowers Fish Tanks and Ponds Blood Swimming pools

Digestion-process by which foods are broken down into simpler substances.

Mechanical digestion-physical process in which food is torn apart (mouth)

Chemical digestion- chemical reactions in which large molecules are broken down into smaller molecules. (stomach and small intestines)

Mouth-pH around 7. Saliva contains amylase, an enzyme which begins to break carbohydrates into sugars.

Stomach- pH around 2. Proteins are broken down into amino acids by the enzyme pepsin.

Small intestine-pH around 8. Most digestion ends. Small molecules move to bloodstream toward cells that use them

mouth

esophagus

stomach

small intestine

large intestine

Digestive system