DO-NOW Name each of the following chemicals in this reaction Na(s) + K 2 SO 4 (aq)  Na 2 SO 4 (aq) + K(s) What does the arrow mean? What do you think the italicized symbols mean? What kind of compound is formed?

Chapter 11 Describing Chemical Reactions

Objectives 11.1a Describe how to write a skeleton equation. 11.1b Describe the steps for writing and balancing a chemical equation.

Chemical Equations In a chemical reaction, one or more reactants change into one or more products These reactions can be written as equations

Word equations Word equations are always written like thus: Reactants  Products Reactants and Products are separated by an arrow ◦ Arrow means “yields”, “gives”, or “reacts to produce”

Example- write a word equation “Iron reacts with oxygen to produce Iron (III) oxide” Iron + Oxygen  Iron (III) Oxide “Hydrogen peroxide decomposes to water and oxygen gas” Hydrogen peroxide  water + Oxygen

In other words Methane reacts with oxygen to yield carbon dioxide and water Methane + Oxygen  Carbon Dioxide + Water

Chemical and Skeleton equations A chemical equation is a representation of the chemical reaction A skeleton equation does not indicate the relative amounts of each substance

Writing skeleton equations To write a skeleton equation, write the chemical symbol for the reactants to the left of the yields sign and the products to the right “Iron reacts with oxygen to produce Iron (III) oxide” Fe(s) + O 2 (g)  Fe 2 O 3 (s) Symbols indicate physical states of substances (s=solid, g=gas)

Catalysts “Hydrogen Peroxide (H 2 O 2 ) will decompose into water and oxygen gas” H 2 O 2 (aq)  H 2 O(l) + O 2 (g) A catalyst is a substance that will speed up a reaction. For instance, Manganese (IV) oxide (MnO 2 ) will speed up the above reaction. H 2 O 2 (aq) H 2 O(l) + O 2 (g) MnO 2

Practice! 1. Water + Potassium  Hydrogen gas + Potassium Hydroxide 2. Aluminum combines with Chlorine gas to form Aluminum Chloride 3. Ethene (C 2 H 4 ) combines with Hydrogen gas to form Ethane (C 2 H 6 ) when catalyzed by Platinum 4. Carbon Dioxide and Water yield Glucose and Oxygen

Write a skeleton equation for the combustion of methane

Write a skeleton equation for the decomposition of sugar Sugar (C 12 H 22 O 11 ) decomposes into carbon and water

Homework Skeleton Equations Worksheet

A Balanced Chemical equation In order to have a correct chemical equation, coefficients need to be used 2H 2 + O 2  2H 2 O A balanced equation is one where each side of the equation has the same amount of atoms and mass is conserved

How to balance chemical equations First, write the skeleton equation Ie: H 2 + O 2  H 2 O Next use coefficients to balance the equation so that it obeys the law of conservation of mass 2H 2 + O 2  2H 2 O The subscript can NEVER be changed! O O O O O O O O O O O O O O O O O O O O O O O O

Give it a try __C + __O 2  __CO 2 __O 2  __O 3 __Al + __CuCl 2  __AlCl 3 + __Cu __Fe + __O 2  __Fe 2 O 3 __CH 4 + __O 2  __CO 2 + __H 2 O

Tips If you are really stuck on a problem, try to put a 2 in front of the largest compound For problems with polyatomic ions, treat the whole ion as a unit If you’re still stuck, MOVE ON!

Homework Balancing Equations Worksheet (available online) (If you don’t think you can download it online, see me after school for a copy)

Do-now: Balance the following: __Ag + __Cu(NO 3 ) 2  __AgNO 3 + __Cu __C 4 H 10 + __O 2  __CO 2 + __H 2 O

Do-now Balance the following: __SnO 2 + __H 2  __Sn + __H 2 O __N 2 + __H 2  __NH 3 __H 2 SO 4 + __Pb(OH) 4  __Pb(SO 4 ) 2 + __H 2 O

11.2 Types of Reactions

Objective 11.2a Identify the five general types of reactions.

5 Types of reactions The five types of reactions include combination, decomposition, single- replacement, double-replacement, and combustion

1. Combination (Synthesis) Combination Reaction: two or more substances react to form a new substance For example: Magnesium reacts with Oxygen to form Magnesium Oxide 2Mg(s) + O 2 (g)  2MgO(s)

Practice What is the product of this combination reaction? (Make sure you balance charges when forming ionic compounds!) Sodium + Diatomic Fluorine  ? __Na + __F 2 

2. Decomposition A Decomposition Reaction is one where a single compound breaks down into two or more substances For Example: Mercury (II) Oxide will form Mercury and Oxygen when heated _HgO(s)  _Hg(s) + _O 2 (g)

Practice What are the products in this decomposition reaction? (Keep diatomic elements in mind!) Calcium Oxide  ? __CaO 

3. Single-Replacement Reaction Single-Replacement Reaction: One element replaces a second element in a compound ◦ Both reactants and products consist of an element and a compound For example: 2Mg(s) + 2HCl(aq)  2MgCl(aq) + H 2 (g)

Activity Series- p. 361 The activity series lists elements in increasing activity A reactive metal will replace a less reactive metal There also is an activity series for nonmetals

Practice What are the products in this Single Replacement reaction? Lithium + Magnesium Chloride  ? __Li + __MgCl  Copper + Iron (III) Nitrate?

4. Double Replacement Reactions Double Replacement Reaction: exchange of positive ions between two compounds For example: 2KI(aq) + Pb(NO 3 ) 2 (aq)  2KNO 3 (aq) + PbI 2 (s)

Practice What are the products in this double replacement reaction? Potassium Chloride + Lead Nitrate  ? __KCl + __Pb(NO 3 ) 2 

5. Combustion Reactions Combustion Reactions: an element or compound reacts with oxygen, often producing energy in the form of light and heat ◦ The combustion of a hydrocarbon (compound containing hydrogen and oxygen) will always produce CO 2 and H 2 O For Example: __C 3 H 8 O + __O 2  __CO 2 + __H 2 O 2869

Predict the Products and Balance the equation Combination: __Na + __O 2  Decomposition: __AlCl 3  Single Replacement: __K + __Ag 2 SO 4 

More Practice Double Replacement: __K 2 CrO 4 + __Ba(NO 3 )  Combustion: __C 7 H 16 +_____ 

Homework Read 11.2 Lesson Check, p. 367

AQUEOUS SOLUTION REACTIONS 11.3

Net Ionic Equations Look at the following double replacement reaction NaCl(aq) + AgNO 3 (aq)  AgCl(s) + NaNO 3 (aq) Anything aqueous can be broken into its ions ◦ complete ionic equations show dissolved ionic compounds as dissociated free ions ◦ Let’s do it!

Net Ionic equations cont. Na + (aq) + Cl - (aq) + Ag + (aq) + NO 3 - (aq)  AgCl(s) + Na + (aq) + NO 3 - (aq) Notice that some reactants are the same as some products? ◦ Na + and NO 3 -, “spectator ions” ◦ If you remove them, you have a net ionic equation

Solubility Rules- p. 372 CompoundsSolubilityExceptions Salts of alkali metals and ammonia SolubleSome lithium compounds Nitrates, ChloratesSolubleFew exceptions SulfatesSolublePb, Ag, Hg, Ba, Sr, and Ca ChloridesSolubleAg, Hg. Pb Carbonates, Phosphates, Chromates, Sulfides, Hydroxides InsolubleAlkali compounds, ammonia

ARE THEY SOLUBLE?

Practice KI + Pb(NO 3 ) 2  ?

Homework Read Chapter 11.3 Lesson Check Due Thursday Finish Labs- Types of Reactions and Activity Series for tomorrow