Hydrogen Ions and Activity

• To test a diagnosis of a patient, the doctor orders several tests (urinalysis, blood banking).

• Results from the test will be expressed in units of pH.

  Purpose of pH scale

  • measure the acidity/basic of solution

  • H+ (hydrogen ion) or H3O+ (hydronium ion) - acid

  • OH- (hydroxide) - base

ACID

• pH is less than 7

• neutralizes bases

• Forms H+ ions in solution

• Corrosive

  • reacts with most metals to form hydrogen gas

• Good conductors of electricity

  • bc of ions generated

• Generate ions

  ex. HNO3 + H3O → H3O+ + NO3

Weak and Strong Acids

Weak Acids

• do not ionize partially:

  ex. Acetic, Boric, Nitrous, Phosphoric, Sulfurous

Strong Acids

• ionize completely:

  ex. Hydrochloric, Nitric; Sulfuric, Hydriodic

Common Acids

• HCl (hydrochloric) stomach acid

• H2SO4 (sulfuric acid) car batteries

• HNO3 (nitric acid) explosives

• HC2H3O2 (acetic acid) vinegar

• H2CO3 (carbonic acid) sodas

• H3PO4 (phosphoric acid) flavorings

BASE

• pH greater than 7

• Feels slippery

• Dissolves fats and oils

• Usually forms OH- ions in solution

• Neutralizes acids

Weak and Strong Base

Weak Bases

• ammonia (NH3)

• urea (CO(NH2)2)

Strong Bases

• sodium hydroxide

• barium hydroxide

• calcium hydroxide

Common Bases

• NaOH (sodium hydroxide) LYE soaps, drain cleaner

• Mg(OH)2 (magnesium hydroxide) antacids

• Al(OH)3 (aluminum hydroxide) antacids, deodorants

• NH4OH (ammonium hydroxide) ammonia

Reaction with Indicators

Measuring pH

• pH meters

• pH paper

  • changes color to indicate a specific pH value

• pH Scale

  • 

• pH of Common Substances

  • 

pH Scale

Relationship between pH and pOH

Formulas:

BUFFERS

• a solution that resists changes in pH when small amounts of acids and bases are added

Types of Acids and Bases

(concepts based on reactions of aqueous solution 1800’s)

Svante Arrhenius developed a concept of acids and bases relevant to reactions in H2O

Arrhenius acid

• produces hydrogen ions in water

Arrhenius base

• produce hydroxide ions in water

broader modern concept of acids and bases were developed later

Bronsted-Lowry acid

• donates a hydrogen ion in a reaction

Bronsted-Lowry base

• accepts a hydrogen reaction

Conjugate acid

• compound formed when a base gains a hydrogen ion

• species formed when a base has accepted proton

Conjugate base

• compound formed when an acid loses a hydrogen ion

• species formed when an acid has donated or removes a proton

ex. Acetic Acid ionizes according to the ff. chemical reaction:

Strong vs. Weak Acids and Bases

1. Strong Acids and Bases

   • Goes 100% ionization

   • normally shown with single-headed arrow

2. Weak Acids and Bases

   • Partially dissociate or ionize, reaching some dynamic equilibrium state.

   • double-headed arrow

   • significant in biological systems

     

Buffer Systems

• Carbonates

  • carbonic acid and bicarbonate ion

• Phosphates

  • sodium dihydrogen phosphate and sodium hydrogen phosphate

• Proteins

  • hemoglobin

    • transports O2 when Inhaled

    • transports CO2 when exhaled

    • Cation (+)

    • Anion (-)