Acid and Base Academic Biology Mr. Luis A. Velazquez
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+] [ H+] 7 14 0 Base Acids
pH Scale in terms of [OH-] [ OH-] [ OH-] 7 14 0 Base Acids
pH Scale Neutral [ OH-] [ H+] [ H+] [ OH-] 7 0 14 [ H+]= [ OH-] Base Acids H2O Equilibrium
A C I D S Some important pH B A S E
Problem • Sea water has a pH of 8.50 • If a substance x has more [H+] than sea water. • Sea water • 8.5 pH more than pH less than Down [H+] Up [H+]
Important information • pH for any living thing is between 6.50 and 7.50 • Blood 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 acid Strong Strong Weak Weak
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 Lab • The anthocyanin turns into: • bright pink in acids • reddish-purple in neutral solutions • green in alkaline or basic solutions.
Cabbage Lab • 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.
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. What are buffers?
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 = Acid B = Base N = Neutral • 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 ____ 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? ___