Acids and Bases Ch. 2 Pre-AP Biology Ms. Haut. Despite strong bonds in water molecules, a portion of bonds break, forming a H + and OH - Despite strong.

Acids and BasesAcids and Bases

Ch. 2Ch. 2

Pre-AP BiologyPre-AP Biology

Ms. HautMs. Haut

Despite strong bonds in water molecules, a Despite strong bonds in water molecules, a portion of bonds break, forming a Hportion of bonds break, forming a H++ and OH and OH--

HH220 0 H H++ + OH + OH--

A compound that A compound that releases Hreleases H++ ions in solution ions in solution is an is an acidacid, and one that , and one that accepts Haccepts H++ ions in ions in solution is a solution is a basebase

Acidity is measured on the pH scale: Acidity is measured on the pH scale: – 0-6.9 is acidic 0-6.9 is acidic – 7.1-14 is basic 7.1-14 is basic – Pure water and solutions that are neither basic Pure water and solutions that are neither basic

nor acidic are nor acidic are neutralneutral, with a pH of 7 , with a pH of 7

2.15 The chemistry of life is 2.15 The chemistry of life is sensitive to acidic and basic sensitive to acidic and basic conditionsconditions

The pH The pH scalescale

Each pH unit represents a tenfold change in concentration of H+

Figure 2.15

pH scale

Acidic solution

Neutral solution

Basic solution

Incr

easi

ng

ly A

CID

IC(H

igh

er c

on

cen

trat

ion

of

H+)

Incr

easi

ng

ly B

AS

IC(L

ow

er

con

cen

trat

ion

of

H+)

NEUTRAL[H+] = [OH–]

Lemon juice; gastric juice

Grapefruit juice

Tomato juice

Urine

PURE WATER

Seawater

Milk of magnesia

Household ammonia

Household bleach

Oven cleaner

Human blood

H+

OH–

pH Indicators: pH Indicators: Cabbage Cabbage JuiceJuice

Boiled cabbage Boiled cabbage creates a bluish creates a bluish juice that can be juice that can be used to test pH used to test pH of substancesof substances http://pbskids.org/zoom/activities/sci/

cabbagejuiceindicato.html

pH IndicatorspH Indicators Cabbage juice responds Cabbage juice responds

like litmus paperlike litmus paper– Indicator turns:Indicator turns:

Red in AcidsRed in AcidsBlue in BasesBlue in Bases

http://www.uni-regensburg.de/Fakultaeten/nat_Fak_IV/Organische_Chemie/Didaktik/Keusch/Grafik/cabbage.gif

http://www.howe.k12.ok.us/~jimaskew/litmus.jpg

pH IndicatorspH Indicators

Other indicators:Other indicators:– pH paperpH paper

– phenolphthaleinphenolphthalein

-turns pink in -turns pink in

presence of presence of basebase

http://www.bio-world.com/images/061036.jpg

http://ull.chemistry.uakron.edu/organic_lab/distribution/dist13.gif

Cells are kept close to pH 7 by Cells are kept close to pH 7 by buffers buffers

Biological fluids contain Biological fluids contain buffersbuffers to maintain a stable pH to maintain a stable pH– pH of blood is 7.4pH of blood is 7.4– Outside of a narrow range, enzymes Outside of a narrow range, enzymes

denature denature && reactions stop (That’s a bad reactions stop (That’s a bad thing!)thing!)

BuffersBuffers are substances that are substances that resist pH change resist pH change

They accept HThey accept H++ ions when they are in ions when they are in excess and donate Hexcess and donate H++ ions when they ions when they are depletedare depleted– Buffers are not foolproofBuffers are not foolproof

Some ecosystems are threatened by acid Some ecosystems are threatened by acid precipitationprecipitation

Acid precipitation is formed when air Acid precipitation is formed when air pollutants from burning fossil fuels pollutants from burning fossil fuels combine with water vapor in the air to form combine with water vapor in the air to form sulfuric and nitric acidssulfuric and nitric acids

2.16 Connection: Acid 2.16 Connection: Acid precipitation threatens the precipitation threatens the environmentenvironment

Figure 2.16A

– These acids can kill fish, damage These acids can kill fish, damage buildings, and injure treesbuildings, and injure trees

– Regulations, new technology, and energy Regulations, new technology, and energy conservation may help us reduce acid conservation may help us reduce acid precipitationprecipitation

Figure 2.16B

AcknowledgementsAcknowledgements Unless otherwise noted, illustrations are credited Unless otherwise noted, illustrations are credited

to Pearson Education have been borrowed from to Pearson Education have been borrowed from BIOLOGY: CONCEPTS AND CONNECTIONSBIOLOGY: CONCEPTS AND CONNECTIONS 4th 4th Edition, by Campbell, Reece, Mitchell, and Taylor, Edition, by Campbell, Reece, Mitchell, and Taylor, ©2003. These images have been produced from ©2003. These images have been produced from the originals by permission of the publisher. the originals by permission of the publisher. These illustrations may not be reproduced in any These illustrations may not be reproduced in any format for any purpose without express written format for any purpose without express written permission from the publisher.permission from the publisher.