Chapter 9: Acids and BasesPrinciples of Earth and Physical SciencesMr. TaylorRainier Jr/Sr High School

AcidsAcids

◦taste sour◦cause indicators to change colors

For example they cause blue litmus to change to red.

◦conduct electricity◦are corrosive and damage materials

Acids form hydronium ions (H3O+)

AcidsStrong acids ionize completely in

water.◦This makes them conduct electricity.

This makes them “electrolytes”.

◦The more they ionize, the stronger the acidity. Sulfuric, hydrochloric, and nitric acids are

strong. Acetic, citric, and formic acids are weak.

BasesBases:

◦have a bitter taste◦feel slippery◦conduct electric currents◦cause indicators to change colors

For example bases cause red litmus to change to blue.

◦can damage skinBases form hydroxide ions (OH-)

BasesStrong bases ionize readily in

water and form many hydroxide ions.◦Potassium, sodium, and calcium

hydroxides are strong bases◦Ammonia and baking soda are weak

bases.

pHpH is a measure of hydronium

ions◦pH scale runs from 0-14.

pH 0-7 is an acid; 7-14 is a base. ph 7 is neutral

Each single digit change of pH is a 10X increase/decrease in hydronium ion concentration.

Acid-Base ReactionsA reaction between an acid and a

base is called a neutralization reaction.

A reaction of a strong acid and a strong base forms water and a salt.◦Salts are combinations of positive and

negative ions (Na+ and Cl-; K+ and I-, etc)Resulting products may be acid,

base, or neutral.

SaltsAlmost any combination of

cations and anions will form a salt.◦Salts are used in the kitchen (salt,

baking soda, detergents), fire extinguishers, fertilizers, film photography, and many other uses.

◦Some salts are critical to maintaining good health Sodium (Na+), Potassium (K+), Calcium

(Ca+2), Phosphate (PO4-3), and others.

Household uses of acids, bases, and saltsSoaps

◦Like dissolves like; oily products cannot be cleaned by water alone. Soaps are large molecules that have a polar end and a non-polar end. The non-polar end surrounds the oil; the polar end dissolves in water.

Detergents are much the same but work better in “hard” water (has dissolved minerals in it).

Household uses of acids, bases, and saltsAmmonia is a useful household

cleaner.Bleach

◦Used as a disinfectant (kills germs).◦Used to remove stains. It doesn’t

remove the stain chemical, it just removes the color.

Acids are useful antioxidants to keep fruit fresh◦Vitamin C (ascorbic acid) and citric

acid

Household uses of acids, bases, and saltsAcidic solutions can tenderize

meat◦Vinegar or lemon juice

Curdling of milk in yogurt and cheese is often achieved with lactic acid.

Drain cleaners are strong bases.

That’s all for now!