Ch.+11+and+12+Period+A

Ch. 11 and 12 Period A Wiki = Editor:James Payne = ==== Ch. 11 and Ch. 12 discuss Chemical Reactions and Stoichiometry. It talks about writing, balancing, classifying, and predicting products of chemical reactions. Ch. 12 talks about arithmetic of equations, interpreting chemical equations, mole ratios, reagants, and yields. ====

Writing Chemical Equations
For example when baking bread the ingredients, flour, salt, yeast, and water would be the reactants and the bread would be the product. hydrogen peroxide -> water + oxygen For example the equation for rusting with symbols for the physical states added is: Fe(s) + O2(g)>Fe2O3(s)
 * Chemical reactions are happening all around us, all the time.[[image:http://www.google.com/url?source=imgres&ct=img&q=http://widayanto84.files.wordpress.com/2010/05/chemical-reaction.gif&sa=X&ei=OISSTZC4B4PTgQeI7o0a&ved=0CAQQ8wc&usg=AFQjCNHpvNj5X0xMwU62V9D9uO4gPRkL1Q width="185" height="190"]]
 * In a chemical reactions on or more substances (the reactants) change into one or more new substances (the products)
 * To write out these reactions chemists us a quick shorthand notation called a chemical equation.
 * Word Equations**
 * To write a word equation, write the names of the reactants to the left of the arrow separatd by plus signs; write th names of the products to the right of the arrow, also separated by plus signs.
 * The word equation describing the rusting of iron is: iron + oxide -> iron(III) oxide
 * Thee word equation for "Hydrogen peroxide decomposes to form water and oxygen gas" would be:
 * Chemical Equations**
 * A chemical equation is a representation of a chemical reaction;the formulas of the reactants (on the left) ar connectd by an arrow with the formulas of the products (on th right)
 * A skeleton equation is a chemical equation that does not indicate the relative amounts of the reactants and products
 * Write the formulas of the reactants to the left of the yields sign (arrow) and the formulas of the products to the right.
 * You can state the physical state of substances by using symbols like (s) for solid, (l) for liquid, (g) for a gas, and (aq) for substance in aqueous.
 * A catalyst is a substance that speeds up the reaction but is not usd up in the reaction and is added to the reaction mixture.
 * It is neither a reactant nor a product
 * Elizabeth Howard pg 324-326**

Balancing Chemical Equations
· This method can be used to balance chemical equations · A Balanced Equation is a chemical equation in which mass is conserved; each side of the equation has the same number of atoms of each element. · Balanced Equations include coefficients, which are small whole numbers that appears in front of a formula in a balanced chemical equation. Coefficients that are equal to 1 are not written · Balanced Equations follow Dalton’s Theory that says atoms are not created nor destroyed; they are only rearranged. · To write a balanced chemical equation, first write the skeleton equation. Then use coefficients to balance the equation so that it obeys the law of conservation of mass. · In all balanced equations, each side of the equation have the same number of atoms of each element. · This is the equation for the burning of hydrogen: o H2 + O2 à H2O o This equation is not balanced because the reactants contain two hydrogen and two oxygen, but the product contains two hydrogen but only one oxygen o The correct balanced equation is 2H2 + O2 à 2H2O
 * An unbalanced equation does not indicate the quantity of reactants needed to make the product.
 * A balanced equation must indicate the kinds of parts required and also the quantities of the parts required.
 * A chemical equation has two parts: the reactants and products
 * A bicycle can be used to demonstrate a balanced chemical equation
 * The reactants are the Frame (F), Wheel (W), Handlebar (H), Pedal (P) and the product is the bicycle
 * F + W + H + P à Bicycle
 * This formula shows the parts necessary to make the bicycle, but not the quantities of each part
 * The correct equation for a bicycle would be F + 2W + H + 2P à FW2HP2

Skeleton equations are also known as unbalanced equations.


= ﻿Group 2 (Co-Editor Becky Hyatt) = = Becky Hyatt pg 330-332 =

__ Classifying Reactions __ (pg 330)

 * the five general types of reaction are combination, decomposition, single-replacement, double-replacement, and combustion

__ Combination Reactions __ (pg 330)

 * a **combination reaction** is a chemical change in which two or more substances react to form a single new substance
 * 2Mg(//s//) + O2(//g//) = 2MgO(//s//)
 * the reactants are Mg and O2 and the product is MgO

__ Conceptual Problem 11.4 __ (pg 331)
Writing Equations for Combination Reactions: Copper and sulfur are the reactants in a combination reaction. Complete the equation for the reaction. Cu(//s//) + S(//s//) = (two reactions possible) Complete and balance this equation fir a combination reaction. Be + O2 =
 * Analyze- identify the relevant concepts
 * determine the formulas for the 2 products and balance the 2 possible equations
 * Solve- apply concepts to this situation
 * write the skeleton equation first, then apply the rules for balancing equations
 * Practice Problem:**

__ Decomposition Reactions __ (pg 332)

 * a **decomposition reaction** is a chemical change in which a single compound breaks down into two or more simpler products
 * 2HgO(//s//) = 2Hg(//l//) + O2(//g//)

__ Conceptual Problem 11.5 __ (pg 332)
Writing the Equation for a Decomposition Reaction: Decomposition reactions that produce gases and heat are sometimes explosive. Write a balanced equation for the following decomposition reaction. H2O(//l//) =(electricity) Complete and balance this decomposition reaction. HI = [] - a link for more help with types of chemical reactions = Single-Replacement Reactions = = Andrea Luongo pg 333-335 =
 * Analyze- identify the relevant concepts
 * balance the equation, remembering that hydrogen and oxygen are both diatomic molecules
 * Solve- apply concepts to this situation
 * write the skeleton equation, then apply the rules for balancing equations
 * Practice Problem:**
 * Single-Replacement Reaction is a chemical change in which one element replaces a second element in a compound.
 * Both the reactants and products contain an element and compound in a single-replacement reaction.
 * When a piece of Potassium mixes with water, it produces hydrogen gas and a large quantity of heat.
 * 2K(//s//) + 2H20(//l//) ---> 2KOH(//aq//) + H2(//q//)
 * When a piece of Zinc placed into Copper nitrate, the reaction is:
 * Zn(//s//) + Cu(NO3)2 (//aq//) ---> Cu(//s//) + Zn(NO3)2 (//aq//)
 * In this reaction, Zinc and Copper change places.
 * Single-Replacement Reaction:**
 * Activity Series of Metals is a list of metals in order of decreasing reactivity.
 * Metals displace with other metals depending on the relative reactivities of the two metals.
 * Active metals in the series can replace any metal below it in that series.
 * A halogen can replace another halogen from a compound.
 * Activity of halogens decreases going down Group 7A of the periodic table.
 * When a less active element is the reactant, then there is no reaction.


 * Activity Series of Metals:**

By Andrea Luongo page 333-335

 * Double-Replacement Reaction is a chemical change involving an exchange of positive ions between two compounds.
 * Double-replacement reaction are also known as double-displacement reactions.
 * This usually takes place between an aqueous solution and a precipitate, gas, or molecular compound.
 * True of Double-Replacement Reactions:
 * ===== One of the products is soluble and the precipatates form a solution. =====
 * ===== One product is a gas. =====
 * ===== One product is a molecular compound. =====

[][|Double-Replacement Reaction]
= Big Dan's Restaraunt pg 336-339 =

[[image:reich-chemistry:image3.jpg width="241" height="252"]]Dan McCormack
Writing Equations for Combustion Reactions
 * ===﻿a combustion raction is a chemical change in which an element or a compoujd reacts with an element or a compound reacts with oxygen often producing energy in the form of heat or light.===
 * === the combustion produces carbon dioxide or else the reaction is not complete ===
 * ==Example 1) C6H6(l) + O2(g) -> CO2(g) +H2O(g)==
 * ==BALANCED EQUATION) 2C6H6(l) + 15O2(g) --> 12CO2(g) + 6H20(l)==

Predicting the Prouducts of a Chemical Equation Page 337

 * In a combustion reaction two or more elements and compounds combine to form a single product
 * In a decomposition reaction a single compound is the reactant and two or more substances are the product

Group 3 (Co-Editor Alex Nunan)
= Christian Cooke pg 342 = Many important chemical reactions take place in water-that is, an aqueous solution. The reactants and one of the products separate into cations and anions when they dissolve in water complete ionic equation- equation that shows dissolved ionic compounds as dissociated free ions

EX: Ag+ (aq) + NO3 - (aq) + Na+(aq) + Cl-(aq) ---> AgCl (s) + Na+(aq) + NO3-(aq)

** key terms: **
__ spectator ion- __ an ion appears on both sides of an equation and is not directly involved in the reaction:

__ net ionic equation- __ an equation for a reaction in a solution that shows only those particles that are directly involved in the chemical change:
 * balanced net ionic equations must have a balanced ionic charge

**sample:**
Ag+(aq) + Cl-(aq) --> AgCl(s)
 * net ionic charge on each side is zero, so the equation is balanced

Pb(s) + AgNO3(aq) --> Ag(s) + Pb(NO3)2(aq) Pb(s) + Ag+(aq) --> Ag(s) + Pb2+(aq) Pb(s) + 2Ag+(aq) --> 2Ag(s) + Pb2+(aq)
 * this is the //skeleton equation// for the reaction of lead with silver nitrate
 * this is the //net ionic equation,// unbalanced
 * this is the final balanced equation. It can be balanced by simply adding a coefficient of 2 in front of the Ag+(aq).

**//A net ionic equation shows only those particles involved in the reaction and is balanced with respect to both mass and charge.//**
Watch this video for more help! http://www.youtube.com/watch?v=I2liasSXCXM

Predicting the Formation of Precipitates
· Mixing two ionic compounds can sometimes form **precipitates** · Not all solutions form participates · **Key Note –** You can predict the formation of a precipitate by using the rules of solubility of ionic compounds.


 * Solubility Rules for Ionic Compounds**
 * **Compounds** || **Solubility** ||
 * Salts and alkali metals and ammonia || Soluble ||
 * Nitrate salts and chlorate salts || Soluble ||
 * Sulfate salta except compounds with Pb2+, Ag+, Hg22+, Ba2+, Sr2+, and Ca2+ || Soluble ||
 * Chloride salts except compound with Ag+, Pb2+, and Hg22+ || Soluble ||
 * Carbonates, phosphates, chromates, sulfides, and hydroxides || Most are insoluble ||


 * When compounds are insoluble, they can form precipitates.

Here is a work sheet and answer key to help give you some examples on how to tell which product of a reaction will be a percipitate.

= Group 4 (Co-Editor Peter Hamill) = = PJ Hamill page 353 = = ﻿Caroline Rubino page 354-355 = =__ Using Balenced Chemical Equations __= =__ Stoichiometry __= = Mike Hanley page 356-358 =
 * ====-Nearly Everything you use is manufactured form chemicals - soaps, shapoos, CDs, cosmetics, medicines and cloths====
 * ====The chemical process used in manufacturing must be carried out economically, which is where balenced equations help====
 * ====A balenced chemical equation tells you what amounts of reactants to mix and what amounts of product to expect. (how much to put into the mixture and how much will be produced.)====
 * [[image:http://t3.gstatic.com/images?q=tbn:ANd9GcQHhsqYqMk6oYm9t6fnjDScevAZw_g-prgKlxFik5KLmMQA8iGZ width="290" height="120" caption="This is an example of a balenced equataion"]]
 * [[image:http://www.chemistry-react.org/imageLibrary/jpeg200/172.jpg width="200" height="111"]]
 * ====Chemists use balanced chemical equations as a basis to caculate how much reactant is needed or product is formed in a reaction.====
 * ====When you know the quantity of one substance in a reaction, you can caculate the quantity of any other substance consumed or created in a reaction.====
 * ==== * Quantity - the amounts of a substance expressed in grams or moles* could also be in liters, rons or molecules ====
 * ==== - Stoichiometry - the calculation of quantities in chemical reactions is a subject of chemistry called stoichiometry====
 * ====Caculations using balanced equations are called Stoichiometric calculations====
 * ====Chemists can track reactants and products in a reaction by stoichiometry.====
 * ====It allows chemists to tally the amounts of reactants and products using ratios of moles or pepresentative particles====
 * Below is a video explaining how to do stoichiometry....it is basically a more complex version of what we have been doing in class and is a good video to watch.
 * []

__ Interpreting Chemical Equations __

 * The balanced chemical equation tells you the relative amounts of reactants and products in the reaction
 * **Key concept**: A balanced chemical equation can be interpreted in terms of different quantities, including number of atoms, molecules, or moles; mass; and volume
 * Your interpretation of the equation depends on how you quantify the reactants and the products
 * In the following explanations of interpreting chemical equations, ammonia will be used as an example to make it easier to understand
 * Ammonia is most commonly used as a fertilizer



. N2 + 3H2 à 2NH3
 * Ammonia is produced industrially by the reaction of nitrogen with hydrogen, below is the chemical equation for this reaction

Number of Atoms

 * For the atomic level, a balanced equation indicates that the number and type of each atom that makes up each reactant also makes up each product
 * Both the number and the types of atoms are not changed in reactions
 * In the synthesis of ammonia, the reactants consist of 2 nitrogen atoms and 6 hydrogen atoms, these 8 atoms are recombined in the product

** Number of Molecules **

 * For molecules, the balanced equation indicates that one molecule of nitrogen reacts with the three molecules of of hydrogen
 * Nitrogen and hydrogen will always react to form ammonia in a 1:3:2 ratio
 * You can also take Avogadro's number of nitrogen molecules and make them react with three times Avogadro's number of hydrogen molecules

** Moles **

 * A balanced equation also tells you the number of moles of reactants and products
 * The coefficients of a balanced equation indicate the relative numbers of the moles of the reactants and products in a chemical reaction, this is the most important information that a balanced chemical equation can provide for you, using this information, you can calculate the amounts of reactants and products
 * In the synthesis of ammonia, one mole of nitrogen molecules reacts with three moles of hydrogen molecules to form two moles of ammonia molecules, as you can tell, the number of moles in the reactant doesn't equal the total number of moles in the product

** Mass **

 * ======Balanced chemical equations have to follow the laws of conservation of matter======
 * The number and types of atoms doesn't change in a chemical reaction, therefore, the total mass of the atoms in the reaction doesn't change either
 * The mass of 1 mol of N2 (28 grams) plus the mass of 3 mol of H2 (6 grams) equals the mass of 2 mol of NH3 (34 grams)

** Volume **
**__ Mass Conservation in Chemical Reactions __** Chart for Interpreting Chemical Equations = ﻿Group 5 (Co-Editor Brandon Boisclair) = = Evan Sommerich pg 359-361 =
 * 1 mol of any gas at STP occupies a volume of 22.4 L.
 * The equation shows that 22.4 L of N2 reacts with 67.2 L (3 x 22.4 l) of H2. This reaction forms 44.8 L (2 x 22.4 L) of NH3
 * The mass of the reactants equals the mass of the products
 * The number of the the atoms of each type in the reactants equals the number of atoms of each type in the product
 * **Key concept**: Mass and atoms are conserved in every chemical reaction
 * Molecules, formula units, moles, and volumes may not necessarily be conserved, however they could be.
 * As an example, use hydrogen iodide: H2 + I2 à 2HI
 * In this reaction, molecules, moles, and volume are all conserved, but in most chemical reactions, they arent
 * Here is a good link for more information on Interpreting Chemical equations, and other topics involving stoichiometry:
 * []

Writing and Using mole Ratios
Mole ratio- a conversion factor that derived from the coefficients of a balanced Chemical equation interpreted in terms of moles. [] - a link that may help with the mole calculations.

Brandon Boisclair page 365-367
SAMPLE PROBLEM:

Nitrogen monoxide and oxygen gas combine to form the brown gas nitrogen dioxide, which contributes to photochemical smog. How many liters of nitrogen dioxide are produced when 34 L of oxygen reacts with an excess of nitrogen monoxide?

2NO(g) + O2(g) -> 2NO2(g)

DON'T FORGET: 1. Analyze -List the known and the unknown KNOWN: -Volume of Oxygen = 34 L O2 -2 mol NO2/ 1 mol O2 (Mole ratio from balanced equation) -1 mol O2 = 22.4 L O2 -1 mol NO2 = 22.4 L O2 2. Calculate- Solve for the unknown

34 L O2 X __1 mol O2__ X __2 mol NO2__ X __22.4 L NO2__ = 68 L NO2 22.4 L O2 1 mol O2 1 mol NO2

3. Evaluate- Does the result make sense Because 2 mol NO2 is produced for each 1 mol O2 that reacts, the volume of NO2 should be twice the given volume of O2. The answer should have two significant figures.

= Zoey Killion page 362-364 = __Sample Problems 12.3 (page 362)__ Zoey Killion Finding the Mass of a Product: __Example:__ Calculate the number of grams of NH3 produced by the reaction of 5.40g of hydrogen with an excess of nitrogen. The balanced equation is: N2(g) + 3H2(g) --> 2NH3(g). //Knowns:// //Unkown:// This following series of caluculations can be combined: g H2 --> mol H2 --> mol NH3 --> g NH3 5.04 g H2 X (1 mol H2/ 2.0 g H2) X (2 mol NH3/ 3 mol H2) X (17.0 g NH3/ 1 mol NH3) = **31 g NH3** Because the molar mass of NH3 is substantially greather than the molar mass of H2, the answer should have a larger mass than the given mass. The answer should have two (2) significant figures. //**More Practice Problems:**//
 * 1) Analyze: //List the known and the unkown//
 * 2) Calculate: //Solve for the unknown.//
 * 3) Evaluate: //Does the result make sense?//
 * Step 1:** (Analyze)
 * Mass of hydrogen = 5.40g H2
 * 1 mol H2 = 2.0 g H2 (molar mass)
 * 1 mol NH3 = 17.0 g NH3 (molar mass)
 * mass of ammonia = ? g NH3
 * Step 2:** (Calculate)
 * Step 3:** (Evaluate)
 * 1) Acetylene gas (C2H2) is produced by adding water to calcium carbide (CaC2). CaC2(s) + 2H20(//l//) ---> C2H2(g) + Ca(OH)2(aq). How many grams of acetylene are produced by adding water to 5.00 g CaC2?
 * 2) Using the same equation, determine how many moles of CaC2 are needed to react completely with 49.0 g H20.

__Other Stoichiometric Calculations__: //(page 363)// Zoey Killion In any of these problems, the given quantity is first converted to moles. Then the mole ratio from the balanced equation is used to calculate the number of moles of the wanted substance. Finally, the moles are converted to any other unit of measurement related to the unit mole. __Sample Problems 12.4:__ (page 364) Zoey Killion Calculating the Molecules of a Product: How many molecules of oxygen are produced when a sample of 29.2 g of water is decomposedby electrolysis, as shown in Figure 1? The balanced equation is: 2H20(//l//) --> (//electricity)// 2H2 (g) + O2 (g) //Knowns:// //Unknown:// 2.92 g H2O X (1 mol H20/ 18.0 g H2O) X (1 mol O2/ 2 mol H2O) X (6.02 X 10^23 molecules of O2/ I mol O2) = **4.88 X 10^23 molecules O2** The given mass of water should produce a little less than 1 mol of oxygen, or a little less then Avogadro's number of molecules. The answer should have three (3) significant figures. //The coefficients in a chemical equation indicate the relative number of particles and the relative number of moles of reactants and products. For a reaction involving gaseous reactants or products, the coefficients also indicate relative amounts of each gas. As a result, you can use volume ratios in the same way you ahve used mole ratios.// **For more help with Stoichiometric Calculations watch this video:** **[]**
 * aG (given quantity) -> bW (wanted quantity)
 * 1) Analyze: //List the known and the unkown//
 * 2) Calculate: //Solve for the unknown.//
 * 3) Evaluate: //Does the result make sense?//
 * Example:**
 * Step 1:** (Analyze)
 * mass of water = 29.2 g H20
 * 1 mol H20 = 18.0 g H20 (molar mass)
 * 1 mol O2 = 6.02 X 10^23 molecules of O2
 * molescules of oxygen = ? molecules of O2
 * Step 2:** (Calculate)
 * Step 3:**
 * //More Practice Problems://**
 * 1) How many molecules of oxygen are produced by the decomposition of 6.54 g of potassium chlorate (KClO3)? 2KlO3(s) ---> 2KCl(s) + 3O2(g).
 * 2) The last step in the production of nitric acid is the reaction of nitrogen dioxide with water. 3NO2(g) + H2O//(l)// > 2HNO3(aq) + NO(g). How many grams of nitrogen dioxide must react with water to produce 5.00 X 10^22 molecules of nitrogen monoxide?

=** Group 6 (Co-Editor Haley Conatser) **= = Mitch Martin and Dakota pg 368-371 =

. In a Chemical reaction, an insufficient quantity of any of the reactants will limit the amount of product that forms.

Limiting reagent: reagent that determines the amount of product that can be formed in a reaction.

Excess reagent: Not completely used up in the reaction. = Haley page 372-378 =