ACID AND BASE Mr. Luis A. Velazquez Academic Biology.

ACID AND BASE

Mr. Luis A. Velazquez Academic Biology

What is pH ?pH stands for the potential of Hydrogen

Is the concentration of hydrogen in a given substance.

[ ] is the symbol for concentration.

In other words pH is [H+] in a substance.

What is the pH scale ?

Is a scale that goes from 0 to 14 Any substance above the pH of 7 is

consider a base. Any substance below the pH of 7 is

consider a acid. Any substance at a pH of 7 is not

consider an acid or a base. pH of 7.00 is consider a neutral pH.

What is hydrogen ion?Hydrogen is an positive

ion.Hydrogen is H+

In terms of pH we use [H+]Acids have high [H+]Bases have very low [ H+ ]

What is hydroxide ?Hydroxide is an negative ion.Hydroxide is OH-

In terms of pH we use [OH-]Acids have low [OH-]Bases have very high [OH-]

pH Scale in terms of [H+] [ H+]

Acids Base

714

0

[ H+]

pH Scale in terms of [OH-]

[ OH-]

Acids Base

714

0

[ OH-]

pH Scale

[ H+] [ OH-]

[ H+]=[ OH-]Acids Base

7

14

0

Neutral

H2O

[ OH-] [ H+]

Equilibrium

ACIDS

BASE

Some important pH

ProblemSea water has a pH of 8.50 If a substance x has more [H+] than sea water.

Sea water 8.5

pH less than

pH more than

Up [H+] Down [H+]

Important information pH for any living thing is

between 6.50 and 7.50Blood has a constant pH of 7.4 If the pH goes up to 7.5 your blood will become more alkaline or basic. (basidosis)

If your bloods pH goes down you blood will become more acids. ( Acidosis)

What is an acid ?

An acid pH is to have a number below 7.00.

The smaller the number the more acidic is the substance.

Acids have very high [H+]Acids have very low [OH-]

What is base ?A basic or alkaline pH is to have a number above 7.00.

The greater the number the more alkaline is the substance.

Bases have very low [H+]Bases have very high [OH-]

Stronger and weaker acidStron

g WeakWeakStrong

Understanding Cabbage

The purple color in red cabbage comes from a class of pigment molecules called anthocyanins.

It turns out that anthocyanins are found in flower petals, leaves (it makes them turn red in the fall!) and some fruits such as blueberries.

Anthocyanins are plant pigments known as flavenoids and produce red, pink, violet and magenta colors in the various plant parts.

Cabbage LabThe anthocyanin turns into: bright pink in acids reddish-purple in neutral solutions

green in alkaline or basic solutions.

This water-soluble pigment is also found in apple skin, plums, poppies, cornflowers, and grapes.

Therefore, it is possible to determine the pH of a solution based on the color it turns the anthocyanin pigments in red cabbage juice.

Cabbage Lab

pH 2 4 6 8 10 12

Color Red Pink Violet BlueBlue-Green

Greenish Yellow

Cabbage Lab Analysis

What are buffers?

A substance that eliminates large sudden changes in pH.

Buffers help organisms maintain the pH of body fluids within the narrow range necessary for life. Are combinations of H+ acceptors and donors forms in a solution of weak acids or bases

Work by accepting H+ from solutions when they are in excess and by donating H+ when they have been depleted.

Acids and Bases

An acid is a substance that increases the hydrogen ion concentration in a solution.

Any substance that reduces the hydrogen ion concentration in a solution is a base. Some bases reduce H+

directly by accepting hydrogen ions.

Strong acids and bases

complete dissociate in water.

Weak acids and bases dissociate only partially and reversibly.

Classify the following pH A. 3.90 ____ B. 9.99 ____ C.1.40 ____ D. 2.02 ____ E. 5.78 ____ F. 0.34 ____ G. 8.45 ____ H. 6.30 ____ I. 7.00 ____ J. 13.8 ____ K. 4.08 ____ L. 7.40 ____ M. 1.63 ____

A = Acid B = Base N = Neutral 1. How many acids?

_______ 2. How many bases?_______ 3. Who is the weakest base? ___ 4. Who is the strongest acid? ___ 5. Who is the weakest acid? ___ 6. Who is the strongest base? ___