CHEMISTRY Matter and Change Chapter 9: Chemical Reactions

Table Of Contents Section 9.1 Reactions and Equations CHAPTER9 Table Of Contents Section 9.1 Reactions and Equations Section 9.2 Classifying Chemical Reactions Section 9.3 Reactions in Aqueous Solutions Click a hyperlink to view the corresponding slides. Exit

Reactions and Equations SECTION9.1 Reactions and Equations Recognize evidence of chemical change. chemical change: a process involving one or more substances changing into a new substance Represent chemical reactions with equations. Balance chemical equations. chemical reaction reactant product chemical equation coefficient Chemical reactions are represented by balanced chemical equations.

Reactions and Equations SECTION9.1 Reactions and Equations Chemical Reactions * is called a chemical reaction.

Reactions and Equations SECTION9.1 Reactions and Equations Chemical Reactions (cont.) Evidence that a chemical reaction may have occurred: * Gas bubbles Appearance of a solid

Reactions and Equations SECTION9.1 Reactions and Equations Representing Chemical Reactions Chemists use statements called equations to represent chemical reactions. Reactants are the *. Products are the *. This table summarizes the symbols used in chemical equations.

Reactions and Equations SECTION9.1 Reactions and Equations Representing Chemical Reactions (cont.) In word equations, aluminum(s) + bromine(l) → aluminum bromide(s) reads as “aluminum and bromine react to produce aluminum bromide”. Skeleton equations use symbols and formulas to represent the reactants and products. Al(s) + Br(l) → AlBr3(s) Both word and skeleton equations lack information about how many atoms are involved in the reaction.

Reactions and Equations SECTION9.1 Reactions and Equations Representing Chemical Reactions (cont.) A chemical equation is a statement that uses chemical formulas to *

Reactions and Equations SECTION9.1 Reactions and Equations Balancing Chemical Equations This figure shows the balanced equation for the reaction between aluminum and bromine.

Reactions and Equations SECTION9.1 Reactions and Equations Balancing Chemical Equations (cont.) A coefficient in a chemical equation is the *.

Reactions and Equations SECTION9.1 Reactions and Equations Balancing Chemical Equations (cont.)

Reactions and Equations SECTION9.1 Reactions and Equations Balancing Chemical Equations (cont.)

Reactions and Equations SECTION9.1 Reactions and Equations Balancing Chemical Equations (cont.)

Reactions and Equations SECTION9.1 Reactions and Equations Balancing Chemical Equations (cont.) The most fundamental law in chemistry is the law of conservation of mass. Balanced equations show this law.

Reactions and Equations SECTION9.1 Reactions and Equations Balancing Chemical Equations (cont.)

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions Classify chemical reactions. metal: an element that is a solid at room temperature, a good conductor of heat and electricity, and is generally shiny Identify the characteristics of different classes of chemical reactions.

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions synthesis reaction combustion reaction decomposition reaction single-replacement reaction double-replacement reaction precipitate There are four types of chemical reactions: synthesis, combustion, decomposition, and replacement reactions.

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions Types of Chemical Reactions Chemists classify reactions in order to organize the many types. A synthesis reaction is a reaction in which *.

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions Types of Chemical Reactions (cont.) When two elements react, the reaction is always a synthesis reaction.

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions Types of Chemical Reactions (cont.) In a combustion reaction, * Heated hydrogen reacts with oxygen to produce heat and water in a combustion reaction. This is also a synthesis reaction.

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions Decomposition Reactions A decomposition reaction is one in which *. Decomposition reactions often require an energy source, such as heat, light, or electricity, to occur.

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions Replacement Reactions * is called a single replacement reaction. A + BX → AX + B

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions Replacement Reactions (cont.) A metal will not always replace a metal in a compound dissolved in water because of differing reactivities. An activity series can be used to predict if reactions will occur.

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions Replacement Reactions (cont.) Halogens frequently replace other halogens in replacement reactions. Halogens also have different reactivities and do not always replace each other.

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions Replacement Reactions (cont.) Double replacement reactions occur when *. This figure shows a generic double replacement equation.

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions Replacement Reactions (cont.) * is called a precipitate. All double replacement reactions produce either water, a precipitate, or a gas.

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions Replacement Reactions (cont.) This table shows the steps to write double replacement reactions.

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions Replacement Reactions (cont.) This table summarizes different ways to predict the products of a chemical reaction.

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions Describe aqueous solutions. Write complete ionic and net ionic equations for chemical reactions in aqueous solutions. Predict whether reactions in aqueous solutions will produce a precipitate, water, or a gas. solution: a uniform mixture that might contain solids, liquids, or gases

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions aqueous solution solute solvent complete ionic equation spectator ion net ionic equation Double-replacement reactions occur between substances in aqueous solutions and produce precipitates, water, or gases.

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions Aqueous Solutions An aqueous solution contains one or more * The solvent is the *

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions Aqueous Solutions (cont.) Water is always the solvent in an aqueous solution. There are many possible solutes—sugar and alcohol are molecular compounds that exist as molecules in aqueous solutions. Compounds that produce hydrogen ions in aqueous solutions are acids.

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions Aqueous Solutions (cont.) Ionic compounds can also be solutes in aqueous solutions. When ionic compounds dissolve in water, their ions separate in a process called dissociation.

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions Types of Reactions in Aqueous Solutions When two solutions that contain ions as solutes are combined, the ions might react. If they react, it is always a double replacement reaction. Three products can form: precipitates, water, or gases.

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions Types of Reactions in Aqueous Solutions (cont.) Aqueous solutions of sodium hydroxide and copper(II) chloride react to form the precipitate copper(II) hydroxide. 2NaOH(aq) + CuCl2(aq) → 2NaCl(aq) + Cu(OH)2(s) * are called complete ionic equations. 2Na+(aq) + 2OH–(aq) + Cu2+ (aq)+ 2Cl–(aq) → 2Na+(aq) + 2Cl–(aq) + Cu(OH)2(s)

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions Types of Reactions in Aqueous Solutions (cont.) * are called spectator ions and are not usually written in ionic equations. * are called net ionic equations. 2OH–(aq) + Cu2+(aq) → Cu(OH)2(s)

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions Types of Reactions in Aqueous Solutions (cont.) Some reactions produce more water molecules. No evidence of a chemical reaction is observable. HBr(aq) + NaOH(aq) → H2O(l) + NaBr(aq) Without spectator ions H+(aq) + OH–(aq) → H2O(l).

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions Types of Reactions in Aqueous Solutions (cont.) Gases that are commonly produced are carbon dioxide, hydrogen cyanide, and hydrogen sulfide. 2HI(aq) + Li2S(aq) → H2S(g) + 2LiI(aq)

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions Types of Reactions in Aqueous Solutions (cont.) Another example is mixing vinegar and baking soda, which produces carbon dioxide gas. HCl(aq) + NaHCO3(aq) → H2CO3(aq) + NaCl(aq) H2CO3(aq) decomposes immediately. H2CO3(aq) → H2O(l) + CO2(g)

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions Types of Reactions in Aqueous Solutions (cont.) Two reactions can be combined and represented by a single chemical reaction.

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions Types of Reactions in Aqueous Solutions (cont.) Reaction 1 HCl(aq) + NaHCO3(aq) → H2CO3(aq) + NaCl(aq) Reaction 2 H2CO3(aq) → H2O(l) + CO2(g) Combined equation HCl(aq) + NaHCO3(aq) + H2CO3(aq) → H2CO3(aq) + NaCl(aq) + H2O(l) + CO2(g) Overall equation HCl(aq) + NaHCO3(aq) → H2O(l) + CO2(g) + NaCl(aq)

Reactions and Equations SECTION9.1 Reactions and Equations Study Guide Key Concepts Some physical changes are evidence that indicate a chemical reaction has occurred. Word equations and skeleton equations provide important information about a chemical reaction. A chemical equation gives the identities and relative amounts of the reactants and products that are involved in a chemical reaction. Balancing an equation involves adjusting the coefficients until the number of atoms of each element is equal on both sides of the equation.

Classifying Chemical Reactions SECTION9.2 Classifying Chemical Reactions Study Guide Key Concepts Classifying chemical reactions makes them easier to understand, remember, and recognize. Activity series of metals and halogens can be used to predict if single-replacement reactions will occur.

Reactions in Aqueous Solutions SECTION9.3 Reactions in Aqueous Solutions Study Guide Key Concepts In aqueous solutions, the solvent is always water. There are many possible solutes. Many molecular compounds form ions when they dissolve in water. When some ionic compounds dissolve in water, their ions separate. When two aqueous solutions that contain ions as solutes are combined, the ions might react with one another. The solvent molecules do not usually react. Reactions that occur in aqueous solutions are double-replacement reactions.