Acids, Bases, and Salts Table of Contents Section 2 Reactions of Acids with Bases Section 3 Acids, Bases, and Salts in the Home
What Are Acids? An acid is a compound that dissolves in water to increase the number of hydronium ions, H 3 O +, in solution. An indicator is a compound that can reversibly change color depending on the ph of the solution or other chemical change. An indicator can tell you whether a substance is acidic or basic. For example, acids turn blue litmus paper red.
Acids
What Are Acids? continued An electrolyte is a substance that dissolves in water to give a solution that conducts an electric current. Strong acids ionize completely. Strong acids are strong electrolytes. Weak acids do not ionize completely. Weak acids are weak electrolytes.
What Are Acids? continued Some examples of strong acids: Hydrochloric acid, HCl present in your stomach Sulfuric acid, H 2 SO 4 car batteries; the most-used industrial chemical Nitric acid, HNO 3 used in manufacturing fertilizers and explosives Some examples of weak acids: Acetic acid, CH 3 COOH the acid in vinegar Formic acid, HCOOH the acid in stinging ants Citric acid, H 3 C 6 H 5 O 7 the acid in citrus fruits
Common Acids
What Are Bases? A base is a compound that dissolves in water to increase the number of hydroxide ions, OH, in solution. Strong bases are ionic compounds that contain a metal ion and a hydroxide ion, for example, NaOH, sodium hydroxide. Weak bases, such as ammonia, NH 3, ionize incompletely in water to form hydroxide ions.
Strength and Weakness of Acids and Bases
What is ph? ph is a value used to express the acidity or basicity of a solution. ph values correspond to the concentration of hydronium ions. They also indicate hydroxide ion concentration. A neutral solution, such as pure water, has a ph of 7. An acidic solution has a ph of less than 7. A basic solution has a ph of greater than 7.
ph
ph Scale
What is ph? continued The concentration of a strong acid allows you to calculate ph. When the H 3 O + concentration of a solution can be written as a power of 10, the ph is the negative of the power of 10 used to describe the concentration. Examples: The ph of pure water is 7, so the concentration of H 3 O + in water is 10 7 M. The ph of apple juice is about 3, so the concentration of H 3 O + in water is 10 3 M.
Math Skills Determining ph Determine the ph of a 0.0001 M solution of the strong acid HCl dissolved in water. 1. List the given and unknown values. Given: concentration of HCl in solution = 0.0001 M Unknown: ph 2. Determine the molar concentration of hydroxide ions. HCl is completely ionized into H 3 O + and Cl ions. concentration of H 3 O + = concentration of HCl = 0.0001 M = 1 10 4 M
Math Skills, continued 3. Convert the H 3 O + concentration to ph. concentration of H 3 O + ions = 1 10 4 M ph = ( 4) = 4
What is ph? continued Small differences in ph mean large differences in acidity. Example: the ph of apple juice differs from the ph of coffee by two units, so apple juice is 10 2, or 100, times more acidic than coffee. ph can be measured in more than one way. A more accurate method than the use of indicators is to use an electronic ph meter, which can measure ph very precisely.
Section 2 Reactions of Acids with Bases Acid-Base Reactions A reaction between an acid and a base is a neutralization reaction. Neutralization is an ionic reaction. Example: A strong acid such as HCl ionizes completely in solution: HCl + H 2 O Cl + H 3 O + A strong base such as NaOH ionizes completely in solution: NaOH Na + + OH The total neutralization reaction is the following: Cl + H 3 O + + Na + + OH Na + + Cl + 2H 2 O
Section 2 Reactions of Acids with Bases Neutralization Reaction
Section 2 Reactions of Acids with Bases Acid-Base Reactions, continued Neutralization reactions form water and a salt. A salt is an ionic compound that forms when a metal atom or a positive radical replaces the hydrogen of an acid. Not all neutralization reactions produce neutral solutions. The final ph of the solution depends on: the amounts of acid and base that are combined whether the acid and base are strong or weak
Section 2 Reactions of Acids with Bases Salt
Section 2 Reactions of Acids with Bases Acid-Base Reactions, continued A titration is a neutralization reaction in which the known concentration of one solution is used to determine the unknown concentration of another solution. When the amounts of acid and base added are equal, an equivalence point will be reached. The equivalence point will be at ph 7 for the titration of a strong acid with a strong base, but if a weak acid or base is involved, the equivalence point will not be neutral.
Section 2 Reactions of Acids with Bases Titration
Section 2 Reactions of Acids with Bases Equivalence and End Points
Section 2 Reactions of Acids with Bases Salts To a chemist, a salt can be almost any combination of cations and anions. Common table salt contains sodium chloride, NaCl, which is a salt that is formed from the reaction of hydrochloric acid with sodium hydroxide. Salts are useful substances, and are all around us. Examples: sodium hydrogen carbonate, baking soda silver bromide and silver iodide, in photographic film barium sulfate, sometimes used in taking X rays calcium carbonate, in chalk, limestone, and marble
Section 3 Acids, Bases, and Salts in the Home Cleaning Products Soap improves water s ability to clean because it can dissolve in both oil and in water. This allows oil and water to form an emulsion that can be washed away by rinsing. Soaps are salts of sodium or potassium and fatty acids. When soap combines with certain cations, such as Mg 2+, Ca 2+, and Fe 3+, it can form soap scum. Detergents have replaced soap in many applications because they do not form scum.
Section 3 Acids, Bases, and Salts in the Home Cleaning Products, continued Many household cleaners contain ammonia, a weak base. Solutions of ammonia can clean away light grease smears. Household bleach is a solution of a strong base, sodium hypochlorite (NaOCl). You are probably familiar with bleach s ability to whiten fabrics. Bleach is also a strong disinfectant, a chemical substance that kills harmful bacteria or viruses.
Section 3 Acids, Bases, and Salts in the Home Bleach
Section 3 Acids, Bases, and Salts in the Home Acids, Bases, and Salts in the Household An antacid is a weak base that neutralizes stomach acid. Sodium hydrogen carbonate and magnesium hydroxide (milk of magnesia) are examples. Shampoos are adjusted for an ideal ph. The ph of most shampoos is between 5 and 8. If shampoo is too basic, it can cause strands of hair to swell, giving them a dull, lifeless appearance.
Section 3 Acids, Bases, and Salts in the Home Antacid
Section 3 Acids, Bases, and Salts in the Home Acids, Bases, and Salts in the Household, continued Acids keep fruit fresh longer. Acidic marinades made of vinegar or wine can be used to tenderize meats because they can denature proteins in the meat. Bacteria convert lactose, a sugar in milk, into lactic acid. The lactic acid denatures the protein casein in milk and changes the milk into yogurt. The strong base sodium hydroxide, also called lye, is used to unclog drains.