Chemical Reactions

Chapter 11

A. Introduction to Chemical Equations Chemical Reactions

1. 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 11.1Describing 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 arrowProducts right side of the arrow yields, gives or reacts to produce

Chapter 11.1Describing 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 11.1Describing Chemical Reactions

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 11.1Describing Chemical Reactions

A. Introduction to Chemical Equations4. What are the different symbols used in chemical equations?

Remember the seven diatomic elements:

Chapter 11.1Describing Chemical Reactions

Element SymbolHydrogen H2

Nitrogen N2

Oxygen O2

Fluorine F2

Chlorine Cl2Bromine Br2

Iodine I2

A. Introduction to Chemical Equations5. 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 11.1Describing Chemical Reactions

B. Balancing Chemical Equations

B. Balancing Chemical Equationsb. 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.

1. 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

Chapter 11.1Describing Chemical Reactions

Rules for Writing and Balancing EquationsDetermine 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 sidesTotal number of particles = Coefficient x subscriptBalance 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 formulaCheck 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 11.1Describing Chemical Reactions

B. Balancing Chemical Equations4. What are the rules for writing and balancing equations?

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 11.1Describing 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 11.3Pass out worksheet.

Chapter 11.1Describing Chemical Reactions

A. Classifying Reactions Classifying Reactions

1. What are the five general types of reactions?

a. Combinationb. Decompositionc. Single-replacementd. Double-replacemente. combustion

Chapter 11.2Types 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 11.2Types 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 11.2Types 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 11.2Types 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 11.2Types 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 11.2Types of Chemical Reactions

Chapter 11.2Types of Chemical Reactions

A. Net Ionic Equations Net Ionic Equations

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)

1. 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)

Chapter 11.3 Reactions in Aqueous Solution

1 2 13 14 15 16 17 18+1 +2 +3 -4/+4 -3 -2 -1 0

Chapter 11.3 Reactions in Aqueous Solution

Groups and charges of the families across the Periodic Table

Charges for other sections of the Periodic TableTransition Metals generally have a +2Rare Earth Elements generally have a +3

A. Net Ionic Equation B. Predicting the Formation of a Precipitate

1. 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?

5. Sample Problem 11.8 on page 371

6. Do problems 25 and 26 on page 371.7. Pass out worksheet

Chapter 11.3 Reactions in Aqueous Solution

Compounds Solubility ExceptionsSalts of alkali metals and ammonia

Soluble Some lithium compounds

Nitrate Salts and Chlorate Salts

Soluble Few exceptions

Sulfate Salts Soluble Compounds of Pb, Ag, Hg, Ba, Sr, and Ca

Chloride salts Soluble 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 373K2CO3 (aq) + Sr(NO3)2 (aq) KNO3 ( ) + SrCO3 ( )5. Do the WorksheetTime to study for the test!

Chapter 11.3 Reactions in Aqueous Solution