Good Morning! Please pick up a note packet and chemical equations vocabulary sheet Also take out your reference packets Announcements: I have graded a lot of your work, but PowerSchool was down this weekend for maintenance  Will get them in ASAP Unit 2 Grade Recovery – due by Friday

Chemical Equations

Chemical Equations Chemical equations represent chemical reactions (changes).

All chemical reactions: Have two parts: Reactants - the substances you start with Products - the substances you end up with Reactants ® Products

Describing chemical reactions: Atoms aren’t created or destroyed. The atoms are just rearranged. Can be described several ways - In a sentence: Copper reacts with chlorine to form copper (II) chloride. In a word equation: Copper + chlorine ® copper (II) chloride In formulas: Cu(s) + Cl2(g) ® CuCl2(aq)

Symbols used in equations indicates a reversible reaction. shows that heat is supplied to the reaction. , is used to indicate a catalyst used supplied, in this case, platinum.

What is a catalyst? A substance that speeds up a reaction without being changed by the reaction. Enzymes are biological or protein catalysts.

Reaction Energy All chemical reactions are accompanied by a change in energy.  Exothermic - reactions that release energy to their surroundings (usually in the form of heat). Endothermic - reactions that need to absorb heat from their surroundings to proceed.

Balancing Equations Equations must obey the law of conservation of matter. To balance equations, place numbers in front of elements and compounds (coefficients). NEVER CHANGE SUBSCRIPTS! Counting atoms: Mg3(PO4)2 3 Mg atoms 2 P atoms 8 O atoms

Balancing Equations Al(C2H3O2)3 1 Al atom 6 C atoms 9 H atoms 6 O atoms 3Al2(SO4)3 6 Al atoms 9 S atoms 36 O atoms

Balancing Equations 2 2 ___ H2(g) + ___ O2(g) ---> ___ H2O(l)

Practice 1. Zn + HCl → ZnCl2 + H2 Zn + 2 HCl → ZnCl2 + H2 2. F2 + NaBr → NaF + Br2 F2 + 2 NaBr → 2 NaF + Br2 3. LiCl + O2 → LiClO3 2 LiCl + 3 O2 → 2 LiClO3

Balancing Equations Practice 4. AgNO3 + MgCl2 → AgCl + Mg(NO3)2 5. CaBr2 + K3PO4 → Ca3(PO4)2 + KBr 6. CH4 + O2 → CO2 + H2O 7. C4H10 + O2 → CO2 + H2O 8. MgCO3 → MgO + CO2

ANSWERS 4. 2AgNO3 + MgCl2 →2 AgCl + Mg(NO3)2 5. 3 CaBr2 + 2 K3PO4 → Ca3(PO4)2 + 6 KBr 6. CH4 + 2 O2 → CO2 + 2 H2O 7. 2 C4H10 + 13 O2 → 8 CO2 + 10 H2O 8. MgCO3 → MgO + CO2

Diatomic elements There are 7 elements that never want to be alone. They form diatomic molecules. H2 , N2 , O2 , F2 , Cl2 , Br2 , I2

H N O F Cl Br I

Word Equations Fe2S3 (s) + HCl(g) ® FeCl3 (s) + H2S(g) 1) Solid iron (III) sulfide reacts with gaseous hydrogen chloride to form iron (III) chloride and hydrogen sulfide gas. Fe2S3 (s) + HCl(g) ® FeCl3 (s) + H2S(g) Fe2S3 + 6 HCl ® 2FeCl3 + 3H2S

Word Equations 2) Nitric acid (HNO3) reacts with sodium carbonate to form water, carbon dioxide and sodium nitrate. HNO3 + Na2CO3 ® NaNO3 + H2O + CO2 2 HNO3 + Na2CO3 ® 2 NaNO3 + H2O + CO2

4Ag (s) +2H2S (g) + O2 (g) ®2Ag2S (s) + 2H2O 3) A silver spoon tarnishes. The solid silver reacts with hydrogen sulfide and oxygen in the air to make solid silver sulfide, the black material we call tarnish and water. 4Ag (s) +2H2S (g) + O2 (g) ®2Ag2S (s) + 2H2O

___ Al(s) + ___ Br2(l) →___ AlBr3(s) 4) Aluminum metal reacts with liquid bromine to form solid aluminum bromide ___ Al(s) 2 + ___ Br2(l) 3 →___ AlBr3(s) 2

5 Main Types of Chemical Reactions 1) Synthesis reactions Element + Element →Compound 2Li + Br2  2 LiBr Compound + Compound  Compound SO2 + H2O  H2SO3

A simulation of the reaction: 2H2 + O2 ® 2H2O

Practice Complete and balance the following: H2 + Br2 → Mg + Cl2 → Mg + O2 → K + S → Al + O2 →

Answers H2 + Br2 → 2 HBr Mg + Cl2 → MgCl2 2 Mg + O2 → 2 MgO 2 K + S → K2S 4 Al + 3 O2 → 2 Al2O3

Synthesis Demonstration

Decomposition Reactions decompose = fall apart one compound (reactant) falls apart into two or more elements or compounds. Usually requires energy AB ® A + B 2NaCl 2Na + Cl2 CaCO3 CaO + CO2

Decomposition Reactions A) Binary Compounds Made up of only two elements Breaks apart into its elements H2O → NaCl → HgO →

Decomposition Reactions If the compound has more than two elements you must memorize the products Follow the guide in your packet B) Metallic Carbonates (CO32-) MCO3 → MO + CO2 CaCO3 → CaCO3 → CaO + CO2 Na2CO3 → Na2CO3 → Na2O + CO2

Decomposition Reactions C) Metallic hydrogen carbonate → metallic carbonate + CO2 + H2O MHCO3 → MCO3 + CO2 + H2O NaHCO3 → 2NaHCO3 → Na2CO3 + CO2 +H2O Mg(HCO3)2 → Mg(HCO3)2 → MgCO3 + CO2 + H2O

Decomposition Reactions D) Metallic hydroxides → metallic oxides + water MOH → MO + H2O LiOH → 2LiOH → Li2O + H2O Ca(OH)2 → Ca(OH)2 → CaO + H2O

Decomposition Reactions E) Metallic chlorates → Metallic chlorides + O2 MClO3 → MCl + O2 KClO3 → 2KClO3 →2KCl + 3O2 Mg(ClO3)2 → Mg(ClO3)2 → MgCl2 + 3O2

Decomposition Reactions This is a decomposition reaction that you will do in lab H2O2 → 2H2O2 → 2H2O + O2

Decomposition Reactions Practice: K2CO3 → KHCO3 → KOH → KClO3 → KCl →

Decomposition Demonstration Second Decomposition Demonstration

Single Replacement Also referred to as single displacement One element replaces another Reactants must be an element and a compound. You must use the activity chart to determine if the reaction will occur. Metals will replace metals (and hydrogen). Nonmetals will replace nonmetals.

Single Replacement A + BC ® AC + B 2Na + SrCl2 ® Sr + 2NaCl (metal-metal) F2 + 2LiCl ® 2LiF + Cl2 (nonmetal-nonmetal)

Single Replacement A) Metal- Metal 1. Al + Fe(NO3)2 → 2Al + 3Fe(NO3)2 →2 Al(NO3)3 + 3Fe 2. Ca + AgNO3 → Ca + 2AgNO3 → Ca(NO3)2 + Ag 3. Cu + KCl → Cu + KCl → NR 4. Mg + ZnCl2 → Mg + ZnCl2 → MgCl2 + Zn

Single Replacement B) Metal – H2O Na + H2O → Na + H2O → NaOH + H2 Ca + H2O → Ca + 2H2O → Ca(OH)2 + H2 Ag + H2O → Ag + H2O → NR

Single Replacement C) Metal + Acid (H….) Zn + HCl → Zn + 2HCl → ZnCl2 + H2 Mg + HCl → Mg + 2HCl → MgCl2 + H2 Ca + HNO3 → Ca + 2HNO3 → Ca(NO3)2 + H2 Au + HCl → Au + HCl → NR

Single Replacement D) Nonmetal – Nonmetal Cl2 + HBr → Cl2 + 2HBr → 2HCl + Br2 F2 + CaBr2 → F2 + CaBr2 → CaF2 + Br2 I2 + KF → I2 + KF → NR Br2 + NaCl → Br2 + NaCl → NR

Single Replacement Demonstration Second Single Replacement Demonstration

Combustion 1. CH4 + O2 → CH4 +2O2 ® CO2 + 2H2O A reaction in which a hydrocarbon reacts with oxygen and always produces carbon dioxide and water. Combustion reactions are exothermic 1. CH4 + O2 → CH4 +2O2 ® CO2 + 2H2O

Combustion C3H8 + O2 → C3H8 + 5O2 → 3CO2 + 4H2O C4H10 + O2 → C6H12O6 + O2 → C6H12O6 + 6O2 → 6CO2 + 6H2O

The charcoal used in a grill is basically carbon The charcoal used in a grill is basically carbon. The carbon reacts with oxygen to yield carbon dioxide. The chemical equation for this reaction is C + O2  CO2

Combustion Demonstration Second Combustion Demonstration

Double Replacement AB + CD ® AD + CB ZnS + 2HCl ® ZnCl + H2S Two ions replace each other. Reactants must be two ionic compounds AB + CD ® AD + CB ZnS + 2HCl ® ZnCl + H2S AgNO3 + NaCl ® AgCl + NaNO3

Double Replacement CaCl2 + Li2CO3 → CaCl2 + Li2CO3 → CaCO3 + 2LiCl Na2SO4 + BaCl2 → Na2SO4 + BaCl2 → 2NaCl + BaSO4 HCl + NaOH → HCl + NaOH → NaCl + H2O Pb(NO3)2 + K2Cr2O7 → Pb(NO3)2 + K2Cr2O7 → PbCr2O7 + 2KNO3

Double Replacement Demonstration

Classify the following Synthesis H2 + O2 ® H2O ® Decomposition AgNO3 + NaCl ® Double replacement Zn + H2SO4 ® Single replacement HgO ® Decomposition C4H10 +O2 ® Combustion Mg(OH)2 + H2SO3 ® Double replacement

Summary An equation: Describes a reaction Must be balanced because to follow Law of Conservation of Mass Can only be balanced by changing the coefficients. Has special symbols to indicate state, and if catalyst or energy is required. Can describe 5 different types of reactions.