11+Reactions+and+Equations

= = =Objectives= 11.1 Describing Chemical Reactions 11.2 Types of Chemical Reactions 11.3 Reactions in Aqueous Solution
 * How do you write a word equation?
 * How do you write a skeleton equation?
 * What are the steps in writing a balanced chemical equation?
 * What are the five general types of reactions?
 * How can you predict the products of the five general types of reactions?
 * What does a net ionic equation show?
 * How can you predict the formation of a precipitate in a double-replacement reaction?

=Outlined Notes= 1. In a chemical reaction, one or more reactants change into one or more products. 2. Chemical equations are used to give information quickly to someone about a reaction. a. A word equation is written with the names of the reactants to the right, then after the arrow the names of the products are written. Compounds and elements are seperated by + signs on both sides. b. Reactants --> Products c. The result of a new substance shows that a chemical reaction occurred. a. __Chemical equation__ - a representation of a chemical reaction b. __Skeleton equation__ - a chemical equation that does not indicate how much reactant and product that are in the reaction c. The reactants go to the left of the yield sign or arrow, and the products to to the right. d. __Catalyst__ - a substance that speeds up a reaction without changing the reaction
 * I. Describing Chemical Reactions**
 * A. Writing Chemical Equations**
 * 3. Word Equations**
 * 4. Chemical Equations**

1. To write a balanced equation, first write the skeleton equation. Then use coefficients to balance the equation so it obeys the law of conservation of mass. 2. __Coefficients__ - whole numbers placed in front of the formulas in the equation to balance it 3. __Balanced equation__ - an equation where each side has the same number of atoms of each element 4. Some skeleton equations are already balanced, such as the equation for making carbon dioxide.  ||  ||
 * B. Balancing Chemical Equations**
 * word equation ||  || magnesium || + || oxygen || [[image:http://dl.clackamas.edu/ch104-04/images/rtarrow.gif width="19" height="14" caption="rtarrow.gif (850 bytes)"]] || magnesium oxide ||
 * skeleton equation ||  || Mg || + || O2 || [[image:http://dl.clackamas.edu/ch104-04/images/rtarrow.gif width="19" height="14" caption="rtarrow.gif (850 bytes)"]] || MgO ||
 * <span style="font-family: trebuchet ms,arial,helvetica;">balanced equation || <span style="font-family: trebuchet ms,arial,helvetica;"> || <span style="font-family: trebuchet ms,arial,helvetica;">2 Mg || <span style="font-family: trebuchet ms,arial,helvetica;">+ || <span style="font-family: trebuchet ms,arial,helvetica;">O2 || <span style="font-family: trebuchet ms,arial,helvetica;">[[image:http://dl.clackamas.edu/ch104-04/images/rtarrow.gif width="19" height="14" caption="rtarrow.gif (850 bytes)"]] || <span style="font-family: trebuchet ms,arial,helvetica;">2 MgO ||  ||

-** The five general types of reaction are **__combination__**, **__decomposition__**, **__single-replacement__**, **__double-replacement__**, and **__combustion__**. a. **__Combination Reactions__** 1. **__Combination reaction__**- a chemical change in which two or more substances react to form a single new substance. 2. Combination reaction is also known as synthesis. 3. In all combination reactions, the product is a single substance, which is a compound. - Example: 2Mg+O->2MgO
 * II. Typ****es of Chemical Reactions**
 * A. Classifying Reactions

b **__Decompostion Reactions__** 1. **__Decomposition reaction-__** a chemical change in which a single compound breaks down into two or more simpler products. 2. Decompostition reactions only consist of one reactant and two or more products. 3. The product can be any combination of elements and compounds. 4. Most decomposition reactions require energy in the form of heat, light, and electricity. - Example: 2HgO>2Hg+O

c. **__Single-Replacement Reactions__** 1. **__Single-replacement reaction-__** a chemical change in which one element replaces a second element in a compound. 2. Single-replacement reactions are identifiable ny noting that both the reactants and the products consist of an element and a compound. - Example: 2K+2H2O>2KOH+H and Zn+Cu(NO)--->Cu+Zn(NO) 3.Whether one metal weill displace another metal from a compound depends upon the relative reactivities of the two metals. 4. **__Activity series of metals-__** lists metals in order of decreasing reactivity. 5. A reactive metal will replace any metal listed below it in the activity series.

d. **__Double-Replacement Reactions__** 1. **__Double-replacement reaction-__** a chemical change involving an exchange of positive ions between two compounds. 2. Double-replacement reactions are also refered to as double-displacement reactions. 3. They generaaly take place in aqueous solution and often produce a precipiate, a gas, or a molecular compound such as water. - Example: NaS+Cd(NO)--->CdS+2NaNO - Example: 2NaCN+HSO->2HCN+NaSO - Example: Ca(OH)+2HCL>CaCl+2H2O

e. **__Combustion Reactions__** 1. **__Combustion reactions-__** a chemical change in which an element or a compound reacts with oxygen, often producing energy in the form of heat or light. 2. A combustion reaction always involves oxygen as a reactant and usually the other reactant is a hydrocarbon. - Example: 2CH+25O--->16CO+18HO - Example: 2Mg+O>2MgO - Example: S+O>SO

- The number of elements and/or compounds reacting is a good indicator of possible reaction type and thus possible products. 1. Use this to identify the basic reaction types by using the elements, compounds, and reactants.
 * [[image:http://ase.tufts.edu/premedsociety/chemistry.jpg width="184" height="129" align="left"]]B. Predicting the Products of a Chemical Reaction**


 * III. Reactions In Aqueous Solutions**

A. Net Ionic Equations 1. A net ionic equation shows only those particles involved in the reaction and is balanced with repect to both mass and charge. B. Predicting the Formation of a Precipitate 1. You can predict the formation of a precipitate by using the general rules for solubility of ionice compounds.
 * complete ionic equation- an equation thatt shows dissolved ionic compounds as dissociated free ions.
 * spectator ion- an ion that appears on both sides of an equation and is not directly involved in the reactio.
 * net ionic equation- an equation for a reaction in solutin that shows only those particles that are directly involved in the chemical change.

Additional Notes.
-this is an example of a gas release Reactions take place so atoms can become more stable. -electron configuration Will no take place until needed conditions exist. -activation energy= the anount of energy needed to start a reaction.
 * Recognizing Chemical Reactions**
 * Color Changes- iodine turns red to blue when is reacts with starches
 * Precipitation- liquid solutions create a solid
 * Energy changes- releasing or absorbing heat
 * Odor Changes- rotting food
 * Gas release- bubbles= low rate, explosives= high rate

When a reaction appears to stop The rate at which the products are made in the following reaction is matched by reactants being reformed in a reverse reaction.
 * Equilibrium**

A reaction will appear to stop when the one reactant that is used up.
 * Limiting Reaction**

-many substances will not react unless they are dissolved in water
 * Solubility**
 * __Insoluble__**- materials that cannot be dissolved in water
 * __Soluble__-** materials that can be dissolved in water

Reaction rate is the speed at which a reaction will take place __Factors that increase__ -high temperature -high concentration -presence of catalysts and enzymes -reactants dissolved in a fluid __Factors that decrea__se -presence of inhibitors
 * Reaction Rate**

Amount of substance
 * Concentration**

A substance that speeds up the rate of the reaction without being used up //GENIE BOTTLE// 2H2O > MNO2 > O2 + 2H2O + MNO2 The MNO2 is a //catalyst// and is not really part if the decomposition reaction
 * Catalyst**

Special proteins in organisms that speed up the rate of a chemical reation
 * Enzyme**

A substance that slows down the chemical reation
 * Inhibitor**

=Reference Pages= []

=Practice Problems=

Balance the skeleton equation below. BeCl2 + O2 --> Be(ClO3)2 Reactants

The answers to the balance equations are in pink

1. Balance this equation. Ca(OH)2 + HCl à CaCl2 + H2O Answer: Ca(OH)2 + 2 HCl à CaCl2 + 2 H2O

2. Balance this equation AgNO3 + CaCl2 à Ca(NO3)2 +AgCl Answer: 2 AgNO3 + CaCl2 à Ca(NO3)2 + 2 AgCl

3. Balance this equation Fe2O3 + C à Fe + CO3 Answer: 2 Fe2O3 + 3 C à 4 Fe + 3 CO3 4. Balance this equation NaHCO3 + H2SO4 à Na2SO4 + H2O + CO2 Answer: 2 NaHCO3 + H2SO4 à Na2SO4 + 2 H2O + 2 CO2

5. Balance this equation C4H10 + O2 à CO2 +H2O Answer: 2 C4H10 + 13 O2 à  8 CO2 + 10 H2O 6. Balance this equation Mg(OH)2 + HBr à MgBr2 + H2O Answer: Mg(OH)2 + 2 HBr à MgBr2 + 2 H2O

7. Balance this equation Al2O3 + H2SO4 à Al2(SO4)3 + H2O Answer: Al2O3 + 3 H2SO4 à Al2(SO4)3 + 3 H2O

8 Balance this equation KHCO3 + H3PO4 à K2HPO4 + H2O + CO2 Answer: 2 KHCO3 + H3PO4 à K2HPO4 + 2 H2O + 2 CO2

9 Balance this equation C9H10O + O2 à CO2 + H2O Answer: C9H10O + 14 O2 à 9 CO2 + 10 H2O

Products Because there is more oxygen on the product side, and it is O2, a 3 should be put in front as the coefficient to balance the equation. The final balanced equation is…. BeCl2 + 3O2 --> Be(ClO3)2
 * Be || 1 ||
 * O || 2 ||
 * Cl || 2 ||
 * Be || 1 ||
 * O || 6 ||
 * Cl || 2 ||

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