Acids & Bases

pH pH of a solution is a measure of its hydronium ion (H3O+) concentration 0-14 number scale 7= Neutral Below 7 = Acid Above 7 = Base

pH Scale

Strength of Acids & Bases The strength of an acid or base solution depends on how completely a compound is pulled apart to form ions when dissolved in water. This is called the degree of dissociation or ionization.

Strong pH Water is neutral Closer to 0, the stronger the acid Strong acids: hydrochloric, sulfuric, nitric Closer to 14, the stronger the base Strong bases: sodium hydroxide, potassium hydroxide

Weak pH Weak pH is NEAR the neutral zone (pH =7) Weak acids: acetic, carbonic Weak bases: ammonia, aluminum hydroxide, iron hydroxide

Acids A compound that produces Hydronium ions (H30+) or Hydrogen ions (H+) in water. Acids donate protons Example: HCl + H2O → H30+ + Cl- The reactant HCl is known as hydrochloric acid

Common Acids CH3COOH Acetic acid Vinegar H2CO3 Carbonic acid Carbonated drinks HCl Hydrochloric acid Digestive juices in stomach HNO3 Nitric acid Fertilizer producer H3PO4 Phosphoric acid H2SO4 Sulfuric acid Car batteries

General properties of Acids Sour taste Contain Hydrogen React with metals to produce H gas React with bases to produce salt & water Corrosive Electrolytes (will conduct electricity)

Base A compound that produces hydroxide ions (OH-) when dissolved in water. Ex. NaOH → Na+ + OH-

Properties of Bases Bitter Taste feel slippery to skin Reacts with acids to produce salt & water electrolytes Don’t usually react with metals

Common Bases Ca(OH)2 Aluminum hydroxide Al(OH)3 Deodorant, antacids Calcium hydroxide Ca(OH)2 Concrete, Plaster Magnesium Hydroxide Mg(OH)2 Antacid, laxatives Sodium hydroxide NaOH Drain cleaner, soap production

Always be careful when using acid/base Acid damage Base damage

Indicators Indicator is substance that changes color in the presence of an acid or base In acid, blue litmus paper turns red & phenolphthalein is colorless In a base, red litmus paper turns blue & phenolphthalein is pink Common indicators Examples: litmus paper, pH meter, pH paper, and phenolphthalein.

Formation of Salts Salt- Compound formed from positive ion of a base and a negative ion of an acid Acid + Base Is a neutral substance

Neutralization Reaction of an acid with a base to produce a salt and water (double replacement) HCl + NaOH → H2O + NaCl Whenever deciding if it is a neutralization reaction, look for H2O and a salt, such as NaCl, on the right side of arrow