Ch. 11 Chemical ReactionsWhy: Chemical reactions occur around us all the time. They range from how our bodies produce energy, how we cook, how we make building materials. Understanding these reactions will give you insight into the world around you and help you understand the other sciences you have taken throughout high school

Chemical Reactions

• Chemical Reactions: occur when one or more substances (reactants) changes into one or more new substances (products)

• Remember the signals of a chemical reaction?• a) bubbles- gas formation (NO ADDED HEAT)• b) Temp/Energy Transfer (w/o adding)• c) Color change• d) formation of solid from 2 liquids

Cont.• Word Equations: made of words ex: sodium carbonate

combines with lead (II) nitrate to produce sodium nitrate and lead (II) carbonate.

• Skeletal Equations: a representation of a chemical reaction using formulas and symbols instead of words. They do not indicate the relative amounts of reactants and products. (UNBALANCED) ex: Na2CO3 + Pb(NO3)2

PbCO3 + NaNO3

• Complete Chemical Equations: (Balanced) each side of the equation has the same number of atoms of each element. (Law of Conservation) ex. Na2CO3 + Pb(NO3)2

PbCO3 + 2 NaNO3

Symbols Used

Balancing Chemical Equations• Lets make a Bicycle:• Frame + wheel + handlebar + pedal bicycle

reactants product

Skeletal equation: F + W + H + P FW2HP2

*** IF it was your job to order parts for this bicycle would you be able to do it by using this equation?***

You need a balanced equation to show you the quantity of the materials needed

Remember: You must end with what you began with

Balanced Equation• F + 2W + H + 2P FW2HP2

Coefficients- small whole numbers that are placed in front of the formulas in an equation in order to balance it

Rules for balancing equations

• Determine formulas for reactants and products• Write Skeletal Equation• Balance individual elements using COEFFICIENTS in FRONT of

the formulas. 1 is understood.

• HONClBrIF- exist as diatomic molecules in equations

Guidelines for balancing• 1st = balance polyatomic ions first IFFFFF they appear the

same on both sides

• 2nd = balance metals second, or elements that appear the least in the equation (appear in only one reactant and one product)

• 3rd = non-metals last• C - H - O in that order!

• CHECK EACH ELEMENT OUT on BOTH SIDES OF EQUATION• Ratio of COEFFICIENTS must be lowest ratio!

Before we begin……• How many atoms of each element are in the compound

• NaOH

• Al2(SO4)3

• K2SO4

• 3HCl

• 2Ca3(PO4)2

Balancing Practice• Na + O2 Na2O

• K + Br2 KBr

• KClO3 KCl + O2

• Fe3O4 + H2 Fe + H2O

Counting Atoms Quiz

• 1. On your papers list the diatomic molecules you were to memorize.

• 2. Identify how many atoms of each element are present in the following compounds.

• H3PO4

• 2Ca3(SO4)2

• 3Pb(OH)2

Types of Chemical Reactions

• Combination• Decomposition• Single Replacement• Double Replacement• Combustion

Combination(synthesis, composition)

• chemical change in which two or more substances react to form a SINGLE product

• A + B AB

• Ex: Zn(S) + S(S) ZnS(S)

• non-metals and transition metals can make more than one product! S(s) + O2 (g) SO2 (g) Fe(s) + O2 (g) Fe2O3 (s)

S(s) + O2 (g) SO3 (g) Fe(s) + O2 (g) FeO (s)

Decomposition• A single reactant breaks apart to form two or more

substances. The products may be elements or compounds.• Many compounds react this way when heated(energy used).

• AB A + B

• Ex: 2 H2O2 (l) 2 H2O + O2 (g)

Single Replacement Reaction

• When one element combines with a compound to produce a different single element and compound based on an ACTIVITY SERIES• Single metal replaces the metal in the

compound if it is higher on the activity series (Table 11.2)

• A + BC AC + B

• Ex: Mg(s) + CuCl2 (aq) Cu(s) + MgCl2 (aq)

Will these reactions happen?

• Br2 + NaI -->

• Br2 + NaCl -->

• Fe + Pb(NO3)2 -->

• Ca + H2O-->

• Pb + H2CO3-->

Double Replacement Reaction (double displacement reaction, precipitate reaction)

• There is an exchange of positive ions (cations) between 2 compounds in solution. AB + CD CB + AD **** CB or AD is a solid or a gas OR CB and AD are salt (ionic compound) and water****• 1.One of the products is not soluble and precipitates from solution:• Na2S(aq) + Cd(NO3)2(aq) CdS(s) + 2NaNO3(aq)

• 2. One of the products is a gas:• 2NaCN(aq) + H2SO4(aq) 2HCN(g) + Na2SO4(aq)

• 3. One product is a molecular compound such as water:• Ca(OH)2(aq) + 2HCl(aq) CaCl2(aq) + 2H2O(l)

Cont.

• If two (aq) compounds combine, switch the positive ions and form new compounds

• to determine if one of the resulting compounds is insoluble (A SOLID) follow the solubility guidelines in table 4.1 in your text

• if both compounds are soluble, no reaction occurs

Predict the products

• AgNO3 + NaCl --->

• MgCO3 + K2SO4 --->

• CaCl2 + MgCO3 --->

Combustion reaction

• rapid reactions that produce a flame using O2 as one of the reactants

• HYDROCARBON COMBUSTION1. Complete HC Combustion: when a compound containing hydrogen and carbon reacts with oxygen to produce CO2 and H2O2. Incomplete HC Combustions: when a compound containing hydrogen and carbon reacts with oxygen to produce CO and H2O