Chemical Reactions

Notes #19Chapter 11.1, 11.2, and 11.3

On May 6, 1937, the huge airship Hindenburg erupted into a fireball. Within a short time, 210,000 cubic meters of hydrogen had burned and the airship was destroyed. The chemical reaction that occurred is “hydrogen combines with oxygen to produce water.” You will learn to represent this chemical reaction by a chemical equation.

Word Equations Reactants Products Reactant + Reactant Product + Product Examples:

o Iron + Oxygen Iron (III) Oxideo Hydrogen Peroxide water + oxygeno Methane + oxygen carbon dioxide + water

Word Equations: How could we describe the rusting of

iron?

Useful Information

Chemical Equationso Iron + Oxygen Iron (III) Oxideo Hydrogen Peroxide water + oxygeno Methane + oxygen carbon dioxide + water

What are they as chemical equations? o Fe (s) + O2 (g) Fe2O3 (s)

o H2O2 (aq) H2O (l) + O2(g)

o CH4(g) + O2(g) CO2(g) + H2O(l)

CatalystsA catalyst is a substance that speeds up the reaction but is not used up in the reaction.

Without Catalyst With Catalyst

Balancing Chemical Equations

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

Coefficients are JUST for balancing the equation. Subscripts are used to identify the correct

chemical formula. They DO NOT CHANGE.

Balancing Chemical Equations

Practice:

H2(g) + O2(g) H2O(l)

Al(s) + O2(g) Al2O3(s)

CS2 + Cl2 CCl4 + S2Cl2

P + O2 P4O10 Al + N2 AlN NaNO3 + PbO Pb(NO3)2 + Na2O Fe2O3 + H2 Fe + H2O

Types of Chemical Reactions

Get out 3 pieces of paper Make a flipbook organizer. (See Mrs.

Branum’s!) Space paper 1 inch apart and fold. Staple your organizer Name the organizer: Types of Reactions You have 5 minutes

Page 1: Combination Reactions

General Equation: R +S RS

Reactants: Generally two elements or two compounds COMBINE

Product: A single compound

Example: 2Mg(s) + O2(g) 2MgO(s)

Page 2: Decomposition Reactions

General Equation: RS R + S

Reactants: A single binary compound or compound with a polyatomic ion.

Products: Two or more elements

Example: 2HgO(s) 2Hg(l) + O2(g)

Page 3: Single-Replacement

Reactions General Equation: T + RS TS + R

Reactants: An element and a compound

Products: a different element and a new compound

Example: Zn + AgNO3 Ag + Zn(NO3)2

Page 4: Double-Replacement Reactions

General Equation: R+S- + T+U- R+U- + T+S-

Reactants: Two ionic compounds. They exchange their ions.

Products: Two new compounds. A reaction has occurred when we see a precipitate.

Example: K2CO3(aq) + BaCl2(aq) 2KCl(aq)+ BaCO3(s)

Page 5: Combustion Reactions

General Equation: CxHy + (x+(y/4))O2 xCO2 + (y/2)H2O

Reactants: Oxygen and a compound that contains C and H

Products: CO2 and H2O

Example: CH4(g) + 2O2(g) CO2(g) + 2H2O(g)

Practiceo What type of reaction is described by the following

equation?o Add these examples to your flip organizer in the

appropriate spot!

o 6Li + N2 2Li3N

o 2C8H18(l) + 25 O2(g) 16CO2(g) + 18H2O(l)

o 2NaCN(aq) + H2SO4(aq) 2HCN(s) + Na2SO4(aq)

o 2HgO(s) 2 Hg(l) + O2(g)

o Br2(aq) + NaI(aq) NaBr(aq) + I2(aq)

Beautiful Chemistry Through Reactions

http://www.huffingtonpost.com/2014/10/08/beautiful-chemical-reactions-video-tsinghua_n_5947580.html

What happens when chemistry is used t make ART?

See beautifulchemistry.net for more information

Predicting Products Now that you have learned about some of the

basic reaction types, you can predict the products of many reactions.

Use your flip book as a guide

The number of elements and/or compounds is a good indicator of possible reaction type and thus the possible products. (USE YOUR FLIPBOOK)

Practice Predicting Products

o Predict the products for the following reactions and balance the equations:

o Al + Cl2

o C2H2 + O2 o Ag + HCl o MgCl2

o CaI2 + Hg(NO3)2

o Na2S + Cd(NO3)2

Net Ionic Equations Aqueous solutions It means something is

dissolved in water!

Example: AgNO3(aq) + NaCl(aq) AgCl(s) +

NaNO3(aq)

(aq) means it is dissolved in water.

Why is there a solid? (s) It represents that a reaction has occured.

Whenever a solid is formed, we call this a precipitate

To show this reaction, we do the NET IONIC EQUATION.

Beginning Equation:AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)

Complete Ionic Equation:Ag+(aq) + NO3

-(aq) + Na+(aq) + Cl-(aq)

AgCl(s) + Na+(aq) + NO3-(aq)

Cancel out spectator ions on each side: Never cancel out the solid.

When that happens, you will have your NET IONIC EQUATION

It only shows what is important.

Ag+(aq) + Cl-(aq) AgCl(s)

A REACTION ONLY OCCURS IN AQUEOUS SOLUTIONS WHEN A PRECIPITATE FORMS.

Practice Give the net ionic equation:

o Na3PO4(aq) + FeCl3(aq) NaCl(aq) + FePO4(s)

Why are chemical reactions important?

http://chemistry.about.com/video/What-Is-the-Importance-of-Chemistry-.htm

Article Reading: The Science of Pain

Group Activity:o In groups of 2-4, record 4 ways in which

chemical reactions are important to YOU.

o Be specific. Give specific examples.

Exit Slip Grab a post it! Write your name on the

back.

Explain: two ways in which chemical reactions are important environmentally, globally, ethically, or economically.

Post on classroom door before leaving the classroom.