Acids & Bases They are everywhere.. In your food In your house EVEN IN YOU!!!!!
What is an acid? • An acid is a solution that has an excess of H+ ions. It comes from the Latin word acidus that means "sharp" or "sour". • The more H+ ions, the more acidic the solution.
Properties of Acids • Taste sour • Conduct electricity • Corrosive, which means they break down certain substances. Many acids can corrode fabric, skin, and paper Picture from BBC Revision Bites http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/acids_bases_1.shtml
Properties of Acids • Some acids react strongly with metals and form hydrogen gas • React with bases to form salts and water • Turn blue litmus paper red Picture from BBC Revision Bites http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/acids_bases_1.shtml
Uses of Acids • Acetic acid - vinegar • Citric acid - lemons, limes, & oranges. • Ascorbic acid - Vitamin C which your body needs to function. • Sulfuric acid is used in the production of fertilizers, steel, paints, plastics, and in car batteries. • Hydrochloric acid – stomach acid
What is a base? • A base is a solution that has an excess of OH- ions. • Another word for base is alkali.
Properties of a Base • Feel slippery • Taste bitter • Caustic, which means they break down certain substances. • Conduct electricity. (Think alkaline batteries.)
Properties of a Base • Do not react with metals. • React with acids to produce salts and water. • Turns red litmus paper blue.
Uses of Bases • Bases – found in soaps, ammonia, and many other cleaning products. • The OH- ions interact strongly with substances, such as dirt and grease. • Chalk and oven cleaner contain bases. • Blood is a basic solution.
Acids and Bases – electrical conductors • Acids and bases both can conduct electricity because both contain ions • Ionic solutions are electrolytes - any substance containing free ions that make the substance electrically conductive
pH Scale • pH is a measure of how acidic or basic a solution is. • The pH scale ranges from 0 to 14. • Acidic solutions have pH values below 7 • Solutions with a pH of 0 are very acidic.
pH Scale • A solution with a pH of 7 is neutral. • Pure water has a pH of 7. • Basic solutions have pH values above 7. • Solutions with a pH of 14 are very basic
pH Scale • A change of 1 pH unit represents a tenfold change in the acidity of the solution.
pH Scale • For example, if one solution has a pH of 1 and a second solution has a pH of 2, the first solution is not twice as acidic as the second—it is ten times more acidic.
Weak vs. Strong Acids • Strong acids ionize completely when placed in water. HCl, HNO3, H2SO4, HClO4, HI, HBr • HCl H+ + Cl- • Weak acids do not ionize completely, they remain mostly intact and release fewer H+ ions • CH3COOH ↔CH3COO- + H+
Weak vs. Strong Baces • Strong bases ionize completely when placed in water. NaOH, LiOH, Be(OH)2, Mg(OH)2 • Mg(OH)2 Mg2+ + 2(OH)- • Strong bases remove more H+ ions when they are mixed with water (the OH- ions react with the H + ions) • Weak bases do not ionize completely, they remain mostly intact and release fewer OH- ions and remove fewer H+ ions when they are mixed with water • NH3 + H2O ↔NH4+ + OH-
Acid – Base Reactions • A reaction between an acid and a base is called neutralization. An acid-base mixture is not as acidic or basic as the individual starting solutions.
Acids and Bases react to form salts • When an acid and a base react, H+ ions and OH- ions react to produce water and decrease the concentration of H+ ions • The anions and cations that were connected with the H+ ions and OH- ions react to form salts. • NaOH + HCl Na+ + Cl- + H+ + OH- • NaOH + HCl NaCl + H2O
Acid – Base reactions • Each salt listed in this table can be formed by the reaction between an acid and a base. • Salts are very important chemicals
Serial Dilution • Serial dilution is the stepwise dilution of a substance in solution.