Chapter 11 Chemical Reactions

Chapter 11.1 Describing Chemical Reactions A. Introduction to Chemical Equations Chemical Reactions What is a chemical reaction? It is a process in which substances are changing. 2. How do we show a chemical reactions? We use equation with quick, shorthand notation to convey as much information as possible about what happen in a chemical reaction.

Chapter 11.1 Describing Chemical Reactions A. Introduction to Chemical Equations Chemical Equation 3. What are the two ways to represent chemical reactions in an equation? Word Equation  words are used to represent the substances. Reactants  left side of the arrow Products  right side of the arrow  yields, gives or reacts to produce

Chapter 11.1 Describing Chemical Reactions A. Introduction to Chemical Equations Chemical equation  formulas of the reactants are connected by an arrow with the formulas of the products Skeleton equation  is a chemical equation that does not indicate the relative amounts of the reactants and products.

Chapter 11.1 Describing Chemical Reactions A. Introduction to Chemical Equations 4. What are the different symbols used in chemical equations? Symbol Explanation + Separates two reactants or two products  “yields”, separates reactants from products  Used in place of  for reversible reactions (s), (l), (g) Designates a reactant or product in the solid state, liquid state and gaseous state; placed after the formula (aq) Designates an aqueous solution; the substance is dissolved in water; placed after the formula Heat  Indicates that heat is supplied to the reaction Pt A formula written above or below the yield sign indicates its use as a catalyst

Chapter 11.1 Describing Chemical Reactions Remember the seven diatomic elements: Element Symbol Hydrogen H2 Nitrogen N2 Oxygen O2 Fluorine F2 Chlorine Cl2 Bromine Br2 Iodine I2

Chapter 11.1 Describing Chemical Reactions A. Introduction to Chemical Equations 5. Sample Problem 11.1  Writing a Skeleton Equation Hydrochloric acid reacts with solid sodium hydrogen carbonate. The products formed are aqueous sodium chloride, water, and carbon dioxide gas. Do problems 1 and 2 on page 349 below the sample problem 11.1. Pass out worksheet.

Chapter 11.1 Describing Chemical Reactions B. Balancing Chemical Equations B. Balancing Chemical Equations What is a balanced equation? A chemical reaction in which each side of the equation has the same number of atoms of each element and mass is conserved. 2. How do you write a balanced chemical equation? a. First write the skeleton equation b. Use coefficients to balance the equation so that it obeys the law of conservation of mass. 3. What are coefficients? Small whole numbers that are placed in front of the formulas in an equation in order to balance it.

Chapter 11.1 Describing Chemical Reactions B. Balancing Chemical Equations 4. What are the rules for writing and balancing equations? Rules for Writing and Balancing Equations Determine the correct formulas for all the reactants and products. Write the skeleton equation. Determine the number of atoms of each element in the reactants and products. Count a polyatomic ion as a single unit if it appears unchanged on both sides Total number of particles = Coefficient x subscript Balance the elements one at a time by using coefficients. When no coefficient is written, it is assumed to be 1. Never balance an equation by changing the subscripts in a chemical formula Check each atom or polyatomic ion to be sure that the number is equal on both sides of the equation. Make sure all the coefficients are in the lowest possible ratio.

Chapter 11.1 Describing Chemical Reactions 5. Sample problem 11.2 Balancing a Chemical Equation. Students suspended copper wire in a aqueous solution of silver nitrate. They noticed a deposit of silver crystals on the copper wire when the copper reacted with the silver nitrate. AgNO3 (aq) + Cu(s)  Cu(NO3)2(aq) + Ag(s) Do Problems 3 and 4 on page 352 below sample problem 11.2

Chapter 11.1 Describing Chemical Reactions 6. Sample problem 11.3 Balancing a Chemical Equation. Aluminum is a good choice for outdoor furniture because it reacts with oxygen in the air to form a thin protective coat of aluminum oxide. Al(s) + O2(g)  Al2O3(s) Do Problems 5 and 6 on page 353 below sample problem 11.3 Pass out worksheet.

Chapter 11.2 Types of Chemical Reactions A. Classifying Reactions Classifying Reactions What are the five general types of reactions? Combination Decomposition Single-replacement Double-replacement combustion

Chapter 11.2 Types of Chemical Reactions A. Classifying Reactions Combination Reaction What is a combination reaction? It is a chemical change in which two or more substances react to form a single new substance. It is sometimes called a synthesis reaction.

Chapter 11.2 Types of Chemical Reactions A. Classifying Reactions Decomposition reaction What is a decomposition reactions? It is a chemical change in which a single compound breaks down into two or more simpler products.

Chapter 11.2 Types of Chemical Reactions A. Classifying Reactions Single-replacement reaction What is a single-replacement reaction? It is a chemical change in which one element replaces a second element in a compound. Metals replace metals. Nonmetals replace nonmetals.

Chapter 11.2 Types of Chemical Reactions A. Classifying Reactions Double-replacement What is a double-replacement reaction? It is a chemical change involving an exchange of positive ions between two compounds.

Chapter 11.2 Types of Chemical Reactions A. Classifying Reactions Combustion Reaction What is a combustion reaction? It is a chemical change in which an element or a compound reacts with oxygen, often producing energy in the form of heat and light.

Chapter 11.2 Types of Chemical Reactions

Chapter 11.3 Reactions in Aqueous Solution A. Net Ionic Equations Net Ionic Equations What is a molecular equation? It shows all the substances in complete formula states. Pb (s) + AgNO3(aq)  Ag(s) + Pb(NO3)2(aq) 2. What is a complete ionic equation? It shows all the substance in ions except for solid, liquids, or gases. Pb(s) + Ag+(aq) + NO3-(aq)  Ag(s) + Pb2+(aq) + NO3-(aq) 3. What are spectator ion? An ion that appears on both sides of an equation and is not directly involved in the reaction. 4. What is the net ionic equation? It is an equation for a reaction in solution that shows only those particles that are directly involved in the chemical change. Pb(s) + Ag+(aq) Ag(s) + Pb2+(aq)

Chapter 11.3 Reactions in Aqueous Solution Groups and charges of the families across the Periodic Table 1 2 13 14 15 16 17 18 +1 +2 +3 -4/+4 -3 -2 -1 Charges for other sections of the Periodic Table Transition Metals generally have a +2 Rare Earth Elements generally have a +3

Chapter 11.3 Reactions in Aqueous Solution A. Net Ionic Equation B. Predicting the Formation of a Precipitate 5. Sample Problem 11.8 on page 371 6. Do problems 25 and 26 on page 371. 7. Pass out worksheet What is a precipitate? It is a formation of an insoluble salt. (solid) 2. How can you predict the formation of a precipitate in a double-replacement reaction? By using the general rules for solubility of ionic compounds. 3. What the general rules for solubility?

Chapter 11.3 Reactions in Aqueous Solution Compounds Solubility Exceptions Salts of alkali metals and ammonia Soluble Some lithium compounds Nitrate Salts and Chlorate Salts Few exceptions Sulfate Salts Compounds of Pb, Ag, Hg, Ba, Sr, and Ca Chloride salts Compounds of Ag and some compounds of Hg and Pb Carbonates, Phosphates, chromates, sulfides, and hydroxides Most are insoluble Compounds of the alkali metals and of ammonia

Chapter 11.3 Reactions in Aqueous Solution 4. Sample Problem 11.9 on page 373 K2CO3 (aq) + Sr(NO3)2 (aq)  KNO3 ( ) + SrCO3 ( ) 5. Do the Worksheet Time to study for the test!