The pH ScaleThe pH Scale

Is a substance an Is a substance an acid or a base?acid or a base?

ACIDSACIDS

An acid is a compound that increases An acid is a compound that increases the number of hydrogen ions when the number of hydrogen ions when dissolved in water dissolved in water (H+)(H+)

An acid solution tastes sourAn acid solution tastes sour An acid can change the color of certain An acid can change the color of certain

compoundscompounds

What is an What is an ion?ion?

**An ion is an atom that has **An ion is an atom that has lost or gained an electron lost or gained an electron giving it a positive (+) or giving it a positive (+) or

negative (-) charge.negative (-) charge.

** Charged Atom** Charged Atom

USES OF ACIDSUSES OF ACIDS

Citric acid and ascorbic acid (Vitamin C) Citric acid and ascorbic acid (Vitamin C) are found in orange juiceare found in orange juice

Carbonic acid and phosphoric acid give a Carbonic acid and phosphoric acid give a “bite” to soft drinks“bite” to soft drinks

Acids in your stomach aid in digestionAcids in your stomach aid in digestion Sulfuric acid is the most widely used Sulfuric acid is the most widely used

industrial acid in the world. It is used in industrial acid in the world. It is used in making metals, paper, paints, and making metals, paper, paints, and fertilizers.fertilizers.

BASESBASES A base is any compound that increases A base is any compound that increases

the number of hydroxide ions the number of hydroxide ions (OH-)(OH-) when when mixed with watermixed with water

A base solution tastes A base solution tastes bitterbitter A base solution feels A base solution feels slipperyslippery A base can change the color of certain A base can change the color of certain

compoundscompounds

Uses of BasesUses of Bases Bases are used in soaps Bases are used in soaps (remember, (remember,

bases are bases are slipperyslippery)) Bases are used to make paper, in Bases are used to make paper, in

oven cleaners, and to unclog drainsoven cleaners, and to unclog drains Ammonia is a base and is used in Ammonia is a base and is used in

many household cleanersmany household cleaners

Detecting Acids Detecting Acids and Basesand Bases

You can detect an acid using an You can detect an acid using an indicator.indicator.

INDICATORINDICATOR - A substance that - A substance that changes color in the presence of an changes color in the presence of an acid or a base.acid or a base.

INDICATORSINDICATORS Litmus paper is an indicatorLitmus paper is an indicator An An acidacid turns blue litmus paper turns blue litmus paper redred A A basebase turns red litmus paper turns red litmus paper blueblue

pH ScalepH Scale

Acid Base

0

7

14

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 515

[H[H++] pH] pH

10-14 14

10-13 13

10-12 12

10-11 11

10-10 10

10-9 9

10-8 8

10-7 7

10-6 6

10-5 5

10-4 4

10-3 3

10-2 2

10-1 1

100 0

1 M NaOH

Ammonia(householdcleaner)

BloodPure wateMilk

VinegarLemon juiceStomach acid

1 M HCl

Aci

dic

N

eutr

al

Bas

ic

pH of Common SubstancespH of Common Substances

Timberlake, Chemistry 7th Edition, page 335

Did we Miss something??Did we Miss something?? What happens when the pH of a What happens when the pH of a

substance is 7?substance is 7?

Ans: A pH level of 7 indicates a Neutral Ans: A pH level of 7 indicates a Neutral Substance i.e: Water!Substance i.e: Water!

Why Learn about pH?Why Learn about pH?

What do you think is the pH level of NYC What do you think is the pH level of NYC tap water?tap water?

The pH of a swimming pool must be The pH of a swimming pool must be checked periodically. Why?checked periodically. Why?

Is it important for Lakes & Rivers to Is it important for Lakes & Rivers to maintain a certain pH?maintain a certain pH?

How do Antacids Work?How do Antacids Work?

Normal pH in your stomach is 3Normal pH in your stomach is 3 If your stomach pH drops below 3 you If your stomach pH drops below 3 you

don’t feel so welldon’t feel so well An antacid neutralizes the acid in your An antacid neutralizes the acid in your

stomach and brings the pH up to a 3 or 4stomach and brings the pH up to a 3 or 4

AntacidsAntacids

A base can't neutralize your acid all by itself. A base can't neutralize your acid all by itself. A base needs some chemical "helpers”A base needs some chemical "helpers” All antacids contain at least one of these four All antacids contain at least one of these four

primary ingredients:primary ingredients: * Sodium* Sodium * Calcium* Calcium * Magnesium* Magnesium * Aluminum.* Aluminum.

HOW DO WE HOW DO WE MEASURE MEASURE

pH?pH?

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

ACID BASE

NEUTRAL

The pH Scale

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

ACID BASE

NEUTRAL

The pH Scale

Let’s see what you’ve Let’s see what you’ve learned!learned!

Professor Know-It-Professor Know-It-All wants to know All wants to know what you’ve what you’ve learned. Answer learned. Answer the following the following questions questions carefully.carefully.

QuestionQuestion #1 #1Lemon juice Lemon juice

has a pH of has a pH of 2.2. Is it an 2.2. Is it an acid or a base?acid or a base?

Question #2Question #2

Detergents Detergents such as Tide such as Tide have a pH of have a pH of about 10. Is about 10. Is Tide an acid Tide an acid or a base?or a base?

Question #3Question #3Seawater has Seawater has

a pH of 8.2. Is a pH of 8.2. Is seawater an seawater an acid or a base?acid or a base?

Question #4Question #4The inside of The inside of

your mouth has your mouth has a pH of 7. Is it a pH of 7. Is it an acid or a an acid or a base?base?

Question #5Question #5How do you How do you

think we came think we came up with the up with the term “acid term “acid rain”?rain”?

Question #6Question #6409 cleaner 409 cleaner

contains contains ammonia that ammonia that has a pH of 12. has a pH of 12. What will 409 What will 409 do to red litmus do to red litmus paper?paper?

Question #7Question #7A soft drink has A soft drink has

a pH of 3.2. a pH of 3.2. What will it do What will it do to a piece of to a piece of red litmus red litmus paper?paper?