Acid and base Iman AlAjeyan

Acid-Base Theory

Acids in water solutions show certain properties. They taste sour and turn litmus paper red. They react with metals like zinc to give off hydrogen.

Arrhenus TheoryArrhenus Theory Acid- is any substance that ionizes partially or completely in water to give hydrogen ions Base- Any substance that ionizes in water to give hydroxide ions (OH-) E.g: (NaOH) NaOH ---> Na+ + OH-

Brønsted – Lowry Theory Acid Acid is a substance that can donate a proton (H+) Base Base is a substance that can accept a proton (H+) Acid = H + + base Acid = H + + base

Lewis Acid is a species that accepts a pair of electrons from another species; in other words, it is an electron pair acceptor. Base is any species that donates a pair of electrons to a Lewis acid Lewis

Strong acids and bases complete dissociate in water. Weak acids and bases dissociate only partially and reversibly.

Table of Common Acids - Hydrochloric -Hydrochloric HCl Carbonic - H 2 CO 3 Sulfuric -Sulfuric H 2 SO 4 Acetic -Acetic HC 2 H 3 O 2 Nitric -Nitric HNO 3 Phosphoric - H 3 PO 4 Citric - H 3 C 6 H 8 O 6 Lactic -Lactic HC 3 H 5 O

Table of Common Bases Sodium Hydroxide NaOH Potassium Hydroxide KOH Magnesium HydroxideMg(OH) 2 Calcium HydroxideCa(OH) 2 Ammonium Hydroxide NH 4 OH Ammonia NH 3 Sodium Carbonate Na 2 CO 3 Sodium Phosphate Na 3 PO 4

Conjugate acid base pairs Conjugate base:Conjugate base: the species that remains after an acid has given up a proton Conjugate acid:Conjugate acid: the species that is formed when a base gains a proton

NH 3 + H 2 O  NH OH - conjugate base conjugate acid acid base

In the two examples water first acts as a base, then as an acid. Any species which can both accept and receive protons is called amphiprotic. (also known as amphoteric)

pH Scale The concentration of hydrogen ions in a solution is very important for living things. The concentration of hydrogen ions is commonly expressed in terms of the pH scale. Low pH corresponds to high hydrogen ion concentration and vice versa.

A substance that when added to water increases the concentration of hydrogen ions(lowers the pH) is called an acid. A substance that reduces the concentration of hydrogen ions(raises the pH) is called a base. pH Scale

Measures the degree of acidity (0 – 14) Most biologic fluids are in the pH range from 6 – 8 Each pH unit represents a tenfold difference in the concentration of hydrogen ions (scale is logarithmic) –A small change in pH actually indicates a substantial change in H + and OH - concentrations. –When the concentration of H+ ions in a solution is , the pH is 14. –In pure water, the average concentration of H+ ions is 10 -7

Buffers Solutions which resist changes in pH when a small amount of an acid or base is added, or when the solution is diluted. This is a very useful for maintaining the pH for a reaction at an optimum value.

A buffer solution consists of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. That is we have a weak acid and its salt or a weak base and its salt Buffers

Buffers help organisms maintain the pH of body fluids within the narrow range necessary for life. Buffers 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. Buffers

Buffering Capacity The amount of acid or base that can be added without causing a large change in pH. Physiological buffers Normal blood pH : 7.3 – 7.45 Blood maintain to pH due to presence of buffers in it. Yours buffer system in Blood. Hemoglobin & oxyhemoglobin : 62% H 2 PO - 4 / HPO 2- 4 : 22% Plasma protein: 11% Bicarbonate : 5%

Review 2: Name the acid, base, conjugate acid and base for each reaction. CH 3 NH 2 + H 2 O CH 3 NH OH - H 3 PO 4 + H 2 O H 3 O + + H 2 PO 4 - HC 2 H 3 O 2 + H 2 O H 3 O + + C 2 H 3 O 2 - CH 3 NH H 2 PO 4 - H 3 PO 4 + CH 3 NH 2 base acid conjugate acid conjugate base

Review 2: Name the acid, base, conjugate acid and base for each reaction. H 2 PO OH - HPO H 2 O HCN + H 2 O CN - + H 3 O + NH 3 + H 2 O NH OH - NO HCO 3 - CO HNO 2 acid base acid base acid base conjugate base conjugate acid conjugate base conjugate acid conjugate base conjugate acid