Chapter 11 Section 1 Chemistry Herriman High Chemistry

Essential Questions What are the parts of a chemical equation? How can you tell if an equation is balanced? Why does an equation need to be balanced? How do you balance a chemical equation? Herriman High Chemistry

Chemical Reactions New substances are formed by bonds breaking and new bonds being formed Rearrangement of atoms Herriman High Chemistry

Why do reactions occur? Reactions occur to reach a more stable state. Gain a full set of valence electrons Reach a more stable energy level Herriman High Chemistry

Chemical Equations Representation of a chemical reaction Iron + Oxygen → Rust Reactants Products 2 types Word equations Formula equations Herriman High Chemistry

- Page 321 Products Reactants

Word Equations List the names of reactants and products Reactants on the left and products on the right Ex: Iron metal + oxygen gas → iron III oxide NOTE: + means “reacts with” → means “produces”, “forms”, “yields” etc. Herriman High Chemistry

Formula Equations Use chemical formulas to represent reactants and products Example: Fe (s) + O2 (g)→ Fe2O3 (s) Letter in parenthesis indicates state (s) solid (l) liquid (g) gas (aq) aqueous solution (dissolved in water) Herriman High Chemistry

Law of Conservation of Mass (conservation of Matter) Mass cannot be created or destroyed; can only change forms All chemical reactions and equations MUST obey this law Herriman High Chemistry

Chemical Equations The number of atoms of products and reactants must be equal to one another to follow the law of conservation of mass Herriman High Chemistry

Identifying Compounds Each new element is identified by a capital letter Example: H2SO4 The elements in Sulfuric Acid Hydrogen Sulfur Oxygen

Subscripts C12H22O11 There are 12 atoms of Carbon There are 22 atoms of Hydrogen There are 11 atoms of Oxygen If there is not a subscript listed, it is understood to be 1. Example: NaCl There is one atom of Sodium There is one atom of Chlorine

NaHCO3 HCl Hydrogen – 1 Chlorine - 1 Sodium – 1 Hydrogen – 1 You Practice! NaHCO3 Sodium – 1 Hydrogen – 1 Carbon – 1 Oxygen -3 HCl Hydrogen – 1 Chlorine - 1

There are times you will see a compound with parenthesis There are times you will see a compound with parenthesis. Pb(NO3)2 The 2 after the parenthesis indicates there are two sets of the parenthesis. Pb(NO3) (NO3) So, in counting the atoms, you would have the following: Lead – 1 Oxygen - 6 Nitrogen -2

(NH4)3PO4 Mg(OH)2 You Practice!! Nitrogen – 3 Magnesium – 1 Hydrogen – 12 Phosphorus – 1 Oxygen – 4 Mg(OH)2 Magnesium – 1 Oxygen – 2 Hydrogen – 2

Coefficient 2H2SO4 This means there are 2 compounds of Sulfuric Acid. Think: H2SO4 H2SO4 Counting the atoms: Hydrogen – 4 Sulfur – 2 Oxygen - 8

3H3PO4 2H2O You Practice!! Hydrogen – 9 Hydrogen – 4 Phosphorus – 3 Oxygen - 12 2H2O Hydrogen – 4 Oxygen - 2

Counting Atoms Worksheet Herriman High Chemistry

Identifying Balanced Chemical Equations Identify if the following equations are balanced. Check to see if there are an equal number of each atom on both sides. H2 + O2 → H2O2 MgS + HCl → H2S + MgCl2 NaHCO3 + H2SO4 → Na2SO4 + CO2 + H2O Herriman High Chemistry

Identifying Balanced Equations cont. CH4 + 2 O2 → CO2 + 2 H2O MgO + H2O → Mg(OH)2 H2SO4 + Fe(OH)3 → Fe2(SO4)3 + H2O Herriman High Chemistry

Balancing Rules Write equation with Correct symbols and formulas. Count the number of atoms of EACH type of element on each side of the arrow to see if it is balanced. If unbalanced then balance atoms (one at a time) using coefficients (NEVER change the subscripts of a formula, or insert numbers within a formula) Check work by recounting atoms of each element to make sure the sides are equal. Coefficients should be the lowest possible ratio. Herriman High Chemistry

Tips for Balancing BrINClHOF – gases that are diatomic or that naturally come in pairs Leave single elements until the end to balance If water is involved balance H and O at the end Polyatomic ions can be count like an element when on both sides Always double check your answer Herriman High Chemistry

Sample Problem (Not Balanced) Zn + HCl 2 ZnCl2 + H2 (Not Balanced) Adjust the coefficients NOT the subscripts. Herriman High Chemistry

Practice Problems Zn(C2H3O2)2 + HBr → ZnBr2 + HC2H3O2 Na2O + H2O → NaOH Herriman High Chemistry

Na2SO4 + KCl → NaCl + K2SO4 Ca3(PO4)2 + AgNO3 → Ca(NO3)2 + Ag3PO4 Herriman High Chemistry

Practice Problems Magnesium metal plus oxygen gas produces solid magnesium oxide Copper (II) sulfate solid and aluminum metal yield solid aluminum sulfate and copper metal Dicarbon tetrahydride gas reacts with oxygen gas to produce carbon dioxide gas and water vapor Herriman High Chemistry

Practice problems Gold (III) chromate reacted with rubidium phosphate to produce rubidium chromate and gold (III) phosphate Calcium hydroxide reacted with nickel (II) sulfate to produce calcium sulfate and nickel (II) hydroxide Herriman High Chemistry

Essential Questions What are the parts of a chemical equation? How can you tell if an equation is balanced? Why does an equation need to be balanced? How do you balance a chemical equation? Herriman High Chemistry

Chapter 11 Section 2 Chemistry Herriman High Chemistry

Essential Questions What are the 5 types of chemical reactions? How can you tell which type of reaction is taking place? How can you predict the products of chemical reactions? Herriman High Chemistry

Types of Chemical Reactions 5 Major types of reactions: Combination/synthesis Decomposition Single replacement Double replacement Combustion Herriman High Chemistry

Combination Reactions Combination reaction: two or more reactants combine together to yield one product A + X → AX A and X could be compounds or elements AX is a compound Herriman High Chemistry

Synthesis Reactions (cont) Metals and nonmetals react to form ionic solids 2 Na + Cl2 → 2 NaCl 4 Li + O2 → 2Li2O Metal oxides produce metal hydroxides CaO + H2O → Ca(OH)2 Nonmetal oxides produce oxyacides SO3 + H2O → H2SO4 Herriman High Chemistry

Synthesis Practice Problems Predict the products of the following reactions. Ba + O2 → Mg + Cl2 → CO2 + H2O → BeO + H2O → 2 2 BaO MgCl2 H2CO3 Be(OH)2 Herriman High Chemistry

Decomposition Reactions Decomposition reactions: single reactant breaks down into parts AX → A + X A and X could be either elements or compounds Requires usually heat or catalysis + Herriman High Chemistry

Decomposition Reactions (cont) Binary compounds break into the two elements 2 H2O → 2 H2 + O2 (with electricity) All metals, except Group 1, yield metal oxides and water when heated M(OH)x → MyOz + H2O Ca(OH)2 → CaO + H2O Herriman High Chemistry

Decomposition Reactions (cont) Metals with polyatomic ions containing oxygen PbCO3 → PbO + CO2 Herriman High Chemistry

Decomposition Problems Predict the products and balance. NaCl → Al(OH)3 → Ag2O → Al2(CO3)3 → 2 2 Na + Cl2 2 Al2O3 + 3 H2O 2 4 Ag + O2 Al2O3 + 3 CO2 Herriman High Chemistry

Single Replacement Reactions Single replacement reactions is where an element replaces a different element in a compound. A + BX → B + AX RULE: atom A will only replace atom B if it is MORE REACTIVE than element B. Herriman High Chemistry

For Metals: Use activity series on page 333 to tell which metals are more “active” or “reactive” than others K(s) + NaOH (aq)→ Ag(s) + KNO3 (aq)→ Herriman High Chemistry

For Nonmetals Usually involves Halogens Activity Decreases as you move down a group F2 Cl2 ACTIVITY DECREASES Br2 I2 F2 + AgI→ Herriman High Chemistry

Double Replacement Reactions Double replacement reactions: cations in two compounds switch places. AY + BX → BY + AX AgNO3 + HCl → HNO3 + AgCl Usually happens in solutions and in one of the following ways Herriman High Chemistry

#1 One of new products is a solid (precipitate, ppt) ___Na2S (aq) +__Cd(NO3)2 (aq) → _____(aq) + ____(ppt) Herriman High Chemistry

#2 One product may bubble out as a gas ___NaCN (aq) +___H2SO4 (aq) → ______(aq) + _____(g) Herriman High Chemistry

#3 Products may be covalent compounds like water __CaCO3 (aq) +__HCl (aq) → ____(aq) + ____(l) + ___(g) Herriman High Chemistry

Combustion Reactions Combustion reaction is when something combines with oxygen and releases a large amount of energy as heat or light. Combustion of hydrocarbons results in CO2 and water CxHy + O2 → CO2 + H2O CH4 + 2 O2 → CO2 + 2 H2O Herriman High Chemistry

Chemical Reactions Complete the following equations and identify the type of reaction HBr (l) → CH3CH2OH (l) +O2 (g) → Cl2 + NaBr → FeS (s) + HCl (l) → Al (s) + S (s) → Herriman High Chemistry

Chemical Reactions gallium hydroxide reacts with lithium nitrate nickel (II) reacts with copper (III) sulfate potassium chloride breaks down cobalt (II) reacts with oxygen pentacarbon decahyrdogen reacts with oxygen Herriman High Chemistry

Essential Questions What are the 5 types of chemical reactions? How can you tell which type of reaction is taking place? How can you predict the products of chemical reactions? Herriman High Chemistry

Chapter 11 Section 2 Assignment P 339 #22, 25-26 P 347-349 #49, 52, 59 (not c), 60, 63, 70, 71 Herriman High Chemistry