Properties of Acids & Bases

Honors Bio: 2-3 Solutions

Solution: a mixture of two or more substances uniformly mixed together – can be PHYSICALLY separated. (often clear)◦ Ex: plasma, air, salt water, whipped cream

Solute: the substance dissolved.

Solvent: The dissolving substance; usually the greater amount.

Aqueous Solution: water is the solvent.

Solutions

The separating of a molecule into simpler molecules or ions.

In water, the force of attraction between water molecules (due to its POLARITY) or between water and other molecules is so strong that it can separate and remove atoms.

In water, this results in the formation of OH- and H+ ions (in EQUAL concentrations)

Dissociation

DissociationA very small percentage of the H2O molecules dissociate to form H+ and OH– ions.

Most of the molecules in pure water remain intact as H2O.

An acid is an aqueous solution that contains a greater concentration of H+ ions (compared to OH- ions).

Hydronium ions: form when free H+ ions react with other water molecules.

pH: measures the concentration of H+ ions in a solution.

Acids

Acids taste SOUR pH <7 Litmus RED Weak acids:

◦ Acetic acid (vinegar-CH3COOH)◦ Carbonic acid (H2CO3)◦ Lactic acid

Strong acids: ◦ Hydrochloric Acid (HCl) ◦ Nitric acid (HNO3)◦ Sulfuric Acid (H2SO4)

Acids (cont.)

Strong vs Weak Acids

Weak Acids

Biological Importance

Mostly Weak Acids Biological Importance

Carbonic Acid (H2CO3)

Lactic Acid (CH3CH(OH)COOH)

Formic Acid (HCOOH)

Hydrochloric acid (strong acid)

Sea water, human blood, soft drinks

Active muscles, milk, microorganisms

Poison in stings from ants & nettle plants.

Stomach acid

Bases (Alkaline) An alkaline solution

contains more hydroxide (OH-) than hydrogen (H+) ions.

Bases taste BITTER

Bases feel SLIPPERY

Ph>7 / Litmus turns BLUE Ex: soap, baking soda,

bleach, ammonia, “draino”

Acid + Base Salt + H2O Ex: HCL + NaOH NaCl + H2O

Buffer: chemical substances that neutralize small amounts of acids & bases.

Buffers keep pH constant. Buffers are composed of a weak acid + conjugate base.

Neutralization Reaction

Proteins DENATURE when pH changes

Buffer solutions are necessary to keep the correct pH for enzymes (proteins) in many organisms to work.

Affect of pH on Proteins

Curdled Milk