Acids and Bases . . . . Chapter 10

Acids and Bases are chemical opposites and they both have contrasting properties. Acids are immediately recognizable from their chemical formula in that hydrogen (H) will be the first element listed in the formula. For Example: HCl, H2SO4, H3PO4, etc. Acids almost always have names that end in “__ic acid” For example: HCl = hydrochloric acid H2SO4 = sulfuric acid

Acids will liberate H+ ions when dissolved in water Acids will liberate H+ ions when dissolved in water. It comes from the acidic hydrogen in the formula, which is listed first in the formula. For example: HCl + H2O → H+ + Cl- + H2O Subsequently, each liberated hydrogen ion combines with one molecule of water to form a hydronium ion H+ + H2O → H+3O

Other properties of acids: Acids are corrosive Acids taste sour Acids will neutralize bases Acids will turn blue litmus paper to red

KOH = potassium hydroxide Mg(OH)2 = magnesium hydroxide Characteristics of bases: Bases are recognizable from their formula which usually has a metal followed by hydroxide (OH). For example: NaOH, KOH, Ca(OH)2 Therefore, the name of a typical base has the name of the metal followed by hydroxide: KOH = potassium hydroxide Mg(OH)2 = magnesium hydroxide In aqueous solution, bases will absorb hydrogen ions

Properties of bases: Bases taste bitter or chalky Bases will neutralize acids Bases feel slippery Bases turn red litmus paper to blue Strong bases •are formed from metals of Groups 1A (1) and 2A (2). •include LiOH, NaOH, KOH, and Ca(OH)2.

The strength of an acid or base is measured by pH. pH values rage from ZERO to 14. The more acidic a substance or solution, the lower the pH value. The more basic the substance or solution, the higher the pH value. Any substance or solution having a pH of exactly 7.00 is NEUTRAL.

•is used to indicate the acidity of a solution. The pH of a solution •is used to indicate the acidity of a solution. •has values that usually range from 0 to 14. •is acidic when the values are less than 7. •is neutral with a pH of 7. •is basic when the values are greater than 7. In order to raise the pH value of a solution, you need to add base. In order to lower the pH value of a solution, you need to add acid.

See Page 343

The pH of solutions can be determined using a) pH meter. b) pH paper. c) indicators that have specific colors at different pH values. See Page 339

However, if a solution is buffered, addition of either acid or base will not change the pH. A “BUFFER” is a substance, which, when added to a solution will make that solution resist pH change.

Neutralization Equations See Page 345 - 346 Neutralization Equations In the equation for neutralization, an acid and a base produce a salt and water. acid base salt water HCl + NaOH NaCl + H2O 2HCl + Ca(OH)2 CaCl2 + 2H2O