Notes on Acids and Bases

Properties of Acids:  Taste sour  Conduct electricity (aqueous acids)  Contains H+, (the more H+, the stronger the acid)  Very reactive  Cause indicators to change colors

Uses of Acids:  Metal cleaners  Batteries  Digest food- found in our stomachs  Foods  Paints  Plastics

Examples of Acids:  Hydrochloric acid (HCl)- in stomach  Citric acid (in citrus fruits like lemons)  Acetic acid (vinegar)

Arrhenius Acids  Hydrogen containing compound that ionize hydrogen ions (H+) in aqueous solutions  Monoprotic- acids that contain 1 ionizable hydrogen (nitric acid)  Diprotic- 2 ionizable hydrogens (sulfuric acid)  Triprotic- 3 ionizable hydrogens (phosphoric acid)

Properties of Bases:  Taste bitter (very hazardous)  Contains OH- (the more OH-, the stronger the base)  Typically a solid  Cause indicators to change colors  Slippery when wet  None of the foods we eat are bases, few exceptions (tums, milk of magnesia)

Uses of Bases:  Cleansers  Drain cleaners  Soap  Shampoo  Laundry detergent

Examples of Bases:  Sodium hydroxide (NaOH)  Ammonia  Lime water Ca(OH)2

Arrhenius Bases  Hydroxide containing compound that ionize hydroxide ions (OH-) in aqueous solutions  Amphoteric- can act as an acid or a base

Bronsted-Lowery Acids  Acid is a hydrogen ion (H+) donor  Conjugate base is the particle that remains when the acid donates a hydrogen ion  HCl  Cl- (acid) (conjugate base)

Bronsted-Lowery Bases  Base is a hydrogen ion (H+) acceptor  Conjugate acid is the particle that remains when the acid gains a hydrogen ion  NH 3  NH 4 (Base) (conjugate acid)

Brosted-Lowery Acids/Bases  NH 3 + H 2 O  NH OH -  HCl + H 2 O  H 3 O + + Cl -  H 2 SO 4 + H 2 O  HSO H 3 O +

pH Scale  Ranges from 0-14  Numbers 0-6 represent acids  7 is neutral  Numbers 8-14 represent bases strongest acid strongest base

pH Scale  As you move from pH 0 to pH 6, the concentration of H+ DECREASES (10 times each number)  As you move from pH 8 to pH 14, the concentration of OH- INCREASES (10 times each number)  Ex: A substance with pH3 is 100 times stronger acid than a substance with pH 5. A substance with pH 8 is 100 times weaker base than a substance with pH 10.

pH calculations  pH is the negative logarithm of the hydrogen ion concentration.  pH = -log(H + )  What is the pH of a solution with a hydrogen-ion concentration of 4.2 X ?  What is the pH of a solution with a concentration of (H + ) = 0.045M?

pH calculations cont.  The pH of an unknown solution is What is the hydrogen-ion concentration?  What is the hydrogen-ion concentration of a solution whose pH is 12.83?

pH indicators  Indicators is a valuable tool for measuring pH because its acid form and base form have different colors in solution.  Types of indicators:  pH paper  Bromophenol blue  Methyl red  Phenolphtalein