Acid-Base Theory

Ms. Murray

Let’s start with the theorists!

Lowry Picture Credit: http://www.geocities.com/bioelectrochemistry/lowry.htmBronsted Picture Credit:http://www.geocities.com/bioelectrochemistry/bronsted.htm

Lewis Picture Credit:

http://www.albion.edu/chemistry/CH121/LewisRules.htm

How should we define acids and

bases?

Arrhenius Picture Credit:http://scienceworld.wolfram.com/biography/Arrhenius.html

Arrhenius Model

1884 Acid – a substance that produces H+ ions

(protons) when dissolved in water Sour taste Low pH Turns litmus paper red

Base – a substance that produces OH- ions when dissolved in water Bitter taste Slippery feel High pH Turns litmus paper blue

Arrhenius Picture Credit:http://scienceworld.wolfram.com/biography/Arrhenius.html

Litmus Picture Credit:

http://oldwww.mtlsd.org/senior/science/JPtachcinski/Lab_Proc/Basic%20Science%20Lab%20Techniques.htm

Bronsted-Lowry Model

1923

Acids – proton (H+) donors

Bases – proton acceptors

BronstedLowry

Lowry Picture Credit: http://www.geocities.com/bioelectrochemistry/lowry.htmBronsted Picture Credit:http://www.geocities.com/bioelectrochemistry/bronsted.htm

Painting by E

llen Bronsted

Picture Credit: http://www.geocities.com/bioelectrochemistry/bronsted.htm

Painting by Bronsted (1923)

Lewis Model

Early 1920s

Acid – electron-pair acceptor

Base – electron-pair donor

Lewis Picture Credit:http://www.albion.edu/chemistry/CH121/LewisRules.htm

How do we measure how acidic or basic a compound is?

We measure its…

What is pH?

pH is a number that denotes the hydrogen (hydronium) ion concentration

pOH is a number that denotes hydroxide ion concentration

pH + pOH = 14

If we’re talking about hydrogen ions and hydroxide ions, which theorist should we be thinking about?

Picture Credit:http://scienceworld.wolfram.com/biography/Arrhenius.html

pH Scale

Scale from 1-14

Indicates the H+ concentration of a solution in Moles/L

pH = -log [H+]

http://staff.jccc.net/PD

EC

ELL/chem

istry/phscale.html

pH = -log[H+]

An example:

Given that [H+] = 1.0 x 10^(-7) M, find pH

pH = - log (1.0 x 10^(-7)) = -(-7.00) = 7.00*

*the number of decimal places here = the number of significant figures in the original number

Another example:

pH = -log[H+]

Given a pH of 6.00, calculate [H+] M

[H+] = 10^(-pH)

[H+] =10^(-6.00)

[H+] = 1.0 x 10^(-6.0) M

pH In Your World

The Good - Hydrangea

Picture Credit: http://www.flickr.com/photos/mshades/168884681/

Acceptable Use Policy: http://creativecommons.org/licenses/by/2.0/Picture Credits: http://www.flickr.com/photos/cvalentine/439024324/Acceptable use policy: http://creativecommons.org/licenses/by-nc-nd/2.0/

Picture Credits: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/AcidRain.html

1908 1968

The Bad

A castle in Westphalia, Germany. Built in 1702

Picture Credit: http://www.waterencyclopedia.com/A-Bi/Acid-Rain.html

The Really Ugly!

“And You Will Know Us by The Trail of Dead Fish” - ldandersen

Picture Credit: http://www.flickr.com/photos/ldandersen/181358675/

Acceptable Use Policy: http://creativecommons.org/licenses/by-nc/2.0/Salton Sea

Acid Rain

Damage

Picture Credit: http://www.eco-systems.org/air_pollution_and_dying_forests.htm

-Shenandoah National Park (1997)-- Photo by Bob Winterbottom