The Acid Test

Acids, Bases, and pH

1. What is pH?

pH measures acidity and alkalinity (how basic) a liquid is*

2. Describe the pH Scale

The next few slides will illustrate this point. Be sure to write small

and get it all!

Range of pH scale

•The pH scale ranges from 0 to 14.

•There are no units of measure for pH *

pH Range

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Neutral

[H+]>[OH-] [H+] = [OH-] [OH-]>[H+]

Acidic Basic

Learning Check pH7

Identify each solution as

1. acidic 2. basic 3. neutral

A. _____ HCl with a pH = 1.5

B. _____ Pancreatic fluid pH = 8

C. _____ Sprite soft drink pH = 3.0

D. _____ pH = 7.0

E. _____ pH = 3

F. _____ pH = 12

Solution pH7

Identify each solution as

1. acidic 2. basic 3. neutral

A. _1__ HCl with a pH = 1.5

B. _2__ Pancreatic fluid pH = 8

C. _1__ Sprite soft drink pH = 3.0

D. _3__ pH = 7.0

E. _1__ pH = 3

F. _2__ pH = 12

3. What is a hydronium ion?

Occasionally, in water, a H+ is transferred between H2O molecules

. . . . . . . .H:O: + :O:H H:O:H + + :O:H-

. . . . . . . . H H H

water molecules hydronium hydroxide ion (+) ion (-)

4. How can the pH of a solution be determined?

There will be several slides showing various ways to measure

pH. Be sure to get them all!

Litmus paper

• Litmus paper cannot tell you the exact pH of a substance.

• It can only tell you if it is an acid or a base

• Blue litmus turns pink in the presence of an acid

• Red litmus turns blue in the presence of a base*

pH paper

• pH paper can tell you approximate pH values.

• By placing one end of the pH paper in the solution it will turn a color which can be matched to the color code key. *

Indicators

• Indicators:

• Weak organic acids and bases whose colors differ from the colors of their conjugate acids or bases.

• The color is best viewed from above against a white background

Table of Indicators•      

•Acid / Base Indicators

•Indicator •Lower Color •pH Range •Upper Color

•methyl violet •yellow-green •0.0 - 2.5 •violet

•methyl orange •red •2.5 - 4.4 •yellow

•congo red •blue •3.0 - 5.0 •red

•bromocresol green •yellow •4.5 - 5.5 •blue

•methyl red •red •4.8 - 6.0 •yellow

•bromocresol purple •yellow-green •5.4 - 6.8 •violet

•bromothymol blue •yellow •6.0 - 7.6 •blue

•phenol red •yellow •6.4 - 8.2 •red-violet

•cresol red •yellow •7.1 - 8.8 •violet

•phenolphthalein •colorless •8.3 - 10.0 •dark pink

•Phenolphthalein is a common indicator to use in neutralization titrations. The solution is considered neutral when the solution holds a very faint pink color for half a minute or more.

•alizarin yellow R •yellow •9.9 - 11.8 •dark orange

pH Meter The most precise and

usually more accurate way to measure pH is using a pH meter which directly measures the amount of [H3O+] in the solution

WRITE THE QUESTION AND ANSWER. *

Now Complete the HW--P. 263 #4, 5, & 6

5. What are the properties of an acid?

• Acids• Taste sour• Donate a H+

• pH less than 7• Turn litmus paper red• Turn bromothymol blue to yellow• Turn phenolphthalein colorless • Neutralize bases

6. What are the properties of bases?

• Bases• Taste bitter• Usually ends in -OH• pH greater than 7• Turn litmus paper blue• Turn bromothymol blue to blue• Turn phenolphthalein pink• Feel slippery to touch • Neutralize acids*

Learning Check AB2

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*

Solution AB2

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*

Question of the Day

Describe the solution in each of the following as:

1) acid 2) base or 3)neutral.

A. ___soda

B. ___soap

C. ___coffee

D. ___ wine

E. ___ water

F. ___ grapefruit*

G. ___ rain

H. ___ vinegar

I. ___ saliva

J. ___ salt water

K. ___ ketchup

L. ___ dishwashing detergent

Answers of the Day

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*

G. _1__ rain

H. _1__ vinegar

I. __1_ saliva (depends on what you

ate recently)

J. _3__ salt water

K. __1_ ketchup

L. _2__ dishwashing detergent

7. What compounds are formed when an acid reacts with a base?

When acid and bases with equal amounts of hydrogen ion H+ and hydroxide ions OH- are mixed, the resulting solution is neutral.

NaOH (aq) + HCl(aq) NaCl + H2O

base acid salt water

Ca(OH)2 + 2 HCl CaCl2 + 2H2Obase acid salt water*

Learning Check N2

Select the correct group of coefficients for the

following neutralization equations

A. __ HCl + __ Al(OH)3 __AlCl3 + __

H2O

1) 1, 3, 3, 1 2) 3, 1, 1, 1 3) 3, 1, 1 3

B.__ Ba(OH)2 + __H3PO4 __Ba3(PO4)2 + __ H2O

1) 3, 2, 2, 2 2) 3, 2, 1, 6 3) 2, 3, 1, 6

Solution N2

A. 3HCl + 1Al(OH)3 1AlCl3 + 3H2O

B. 3Ba(OH)2 + 2H3PO4 1Ba3(PO4)2 +

6H2O*

8. Antacids

A practical use of the neutralization process

Antacids

Used to neutralize stomach acid (HCl)

Many contain one or more weak bases

Alka-Seltzer: NaHCO3, citric acid, and aspirin

Di-gel: CaCO3 and Mg(OH)2

Gelusil: Al(OH)3 and Mg(OH)2

Maalox: Al(OH)3 and Mg(OH)2

Mylanta: Al(OH)3 and Mg(OH)2*

More Antacids

Milk of Magnesia: Mg(OH)2

Rolaids: AlNa(OH)2CO3

aluminum sodium dihydroxy carbonate

Tums: CaCO3

Tempo: CaCO3, Al(OH)3, Mg(OH)2*

How much more acidic is a solution of pH 2 than a solution of

pH 6?

A) 3 times more acidic

B) 10 times more acidic

C) 100 times more acidic

D) 1,000 times more acidic

E) 10,000 times more acidic

Answer

• E) 10,000 times more acidic

• Every one pH value that a solution decreases, it is 10 times more acidic

• Example, normal rain is about 5.5. If its pH falls to 4.5 it is now 10 times more acidic.

• Some industrialized areas have had pH values measured to be as low as 2.5 or 1,000 times more acidic

pH measures the concentration of hydrogen ion [H+] in a solution

• So every time you increase one number on the pH scale the acidity (or alkalinity) increases by a power of 10!

• The concentration of pH = 2 solution is 4 pH values from a pH = 6 solution or

• The pH = 2 solution is 10,000 times more acidic than the pH = 6 solution

What does this mean for the environment?

An in-depth look at acid rain

Sources of Acid Rain

Power stations

Oil refineries

Coal with high S content

Car and truck emissions

Bacterial decomposition, and lighting

hitting N2*

Acid Rain

2. Reactions in the atmosphere form SO3

2SO2 + O2 2 SO3*

Acid Rain

3. Reactions with atmosphere water form acids

SO3 + H2O H2SO4 sulfuric acid

NO + H2O HNO2 nitrous acid

HNO2 + H2O HNO3 nitric acid*

Acid Rain4. Effects of Acid Rain

Decline in fish populations in rivers and lasts due to toxic effect of Al leached from soil by acid rain

Extensive fish kills in spring from runoff due to accumulation of large amounts of acid on the snow

Dissolves minerals Mg, Ca, and K from the soil and waxy coatings that protect leaves from bacteria

Corrodes metals, textiles, paper and leather*

Acid Rain

Formation of acid rain:1. Emission of sulfur and nitrogen oxides from

the burning of fuels especially coal with high S content, power stations, oil refineries, vehicles as well as bacterial decomposition, and lighting hitting N2

SO2 26 million tons in 1980

NO and NO2 22 million tons in 1980

Mt. St Helens (1980) 400,000 tons SO2*