UNIT 4: Chemical Reactions – Stoichiometry and Thermodynamics Part B: Chemical Reactions Big Picture Ideas: 1. The identity of the reactants helps scientists to predict the products in a chemical reaction. 2. Quantitative relationships exist with all chemical reactions that allow scientists to predict amounts of products formed, reactants consumed, and percent yield based on theoretical maximum. Big Picture Question: How can you predict the products in a chemical reaction? Suggested Resources Homework Assignments Classwork Assignments Laboratory Activities Formative Assessments Textbook pages: Chapters 11 & 18 Websites: www.webelements.com
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UNIT 4: Chemical Reactions – Stoichiometry and ThermodynamicsPart B: Chemical Reactions
Big Picture Ideas:1. The identity of the reactants helps scientists to predict the products in a chemical reaction.2. Quantitative relationships exist with all chemical reactions that allow scientists to predict amounts
of products formed, reactants consumed, and percent yield based on theoretical maximum.
Big Picture Question: How can you predict the products in a chemical reaction?
Directions: Use this information as a general reference tool to guide you through this unit. Don’t hesitate to ask your teacher for help!
By the conclusion of this unit, you should know the following:
1. There are five basic types of chemical reactions (S, D, SR, DR, Comb.) that exhibit distinct patterns for the prediction of products.
2. Experimental evidence can be used to identify products in a reaction.
3. All reactions follow the Law of Conservation of Matter (balancing equations).
4. Symbols are used to identify different aspects of a chemical reaction (states of matter, catalysts, heat, etc.).
5. Collision theory describes characteristics for a successful reaction.
6. Factors can be altered to affect the rate of a reaction (temperature, surface area, catalyst, concentration).
By the conclusion of this unit, you should be able to do the following:
1. Balance chemical reactions.2. Identify type of chemical reaction.3. Identify if a reaction will occur using an activity series.4. Predict products for a reaction.5. Write balance formula equation given chemical
equation (words).6. Using the collision theory, explain how altering the
temperature, surface area, concentration and the addition of a catalyst affects the rate of a reaction.
1. What type of reaction is it?a. element + element b. ionic compound + ionic compound c. element + ionic compound d. compound e. compound + oxygen
2. How can you tell if a chemical change has taken place? List examples.
3. Define a chemical reaction. Why must we balance chemical equations? (If it is a “must” there is a “law” governing the concept).
4. Balance each reaction below. Identify each type the following reactions are:a) NaOH (aq) + Pb(NO3)2 (aq) NaNO3 (aq) + Pb(OH)2 (s)b) CH4 (g) + O2 (g) CO2 (g) + H2O (l)c) Fe (s) + NaBr (aq) FeBr3 (aq) + Na (s)d) Pb (s) + O2 (g) PbO (g)e) Na2CO3 (s) Na2O (s) + CO2 (g)
5. Complete and balance each reaction below:a) Mg + HCl _________ + ____________b) C2H6 + O2 _________ + ____________c) CaF2 + Na2SO4 _________ + ____________d) Sr + N2 __________
6. List three factors affecting the rate of a chemical reaction. Know why they affect the reaction rate (collision theory!)
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NOTES: CHEMICAL REACTIONSVOCABULARY:
Products
Reactants
+
(s)
(l)
(g)
(aq)
Catalyst
Activation Energy (Ea)
Δ heat
Pt
ENERGY OF CHEMICAL REACTIONS:
Exothermic Reaction: ΔH is negative (–) Endothermic Reaction: ΔH is positive (+)(heat is a “product”) (heat is a “reactant”)
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KINETICS: RATE OF CHEMICAL REACTIONS
The rate of a reaction increases when the # of collisions increases.
Collision Theory:
What factors may cause the # of collisions to increase?
1. Temperature
2. Concentration of the reactants
3. Particle size (surface area) of the reactants4
Energy
Time
Energy
Time
4. Nature of the reactants
5. Adding a catalyst or inhibitor to the reaction
BALANCED CHEMICAL REACTIONS
Law of Conservation of Matter:
WORD FORMULA BALANCED EQUATIONS
1. word equation: hydrogen gas reacts with oxygen gas to form water
formula equation: _______________________________________________
B. Decomposition1. Definition - one single reactant, a compound, breaks apart into two or more simpler products
2. General Form:AB A + B
3. Examples:a. 2 H2O 2 H2 + O2
b. 2 HgO 2 Hg + O2
c. 2 Ag2O 4 Ag + O2
d. CaCO3 CaO + CO2
C. Combustion Reactions1. Definition - oxygen reacts with another substance, often producing energy in the form of heat
and light
2. Types of Combustiona. Complete Combustion
(1) Definition - if sufficient oxygen is present to burn completely(2) Hydrocarbons combine with oxygen to produce carbon dioxide and water
3. General Form (Complete Combustion):CxHy(Oz) + O2 CO2 + H2O
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4. Examples:a. CH4 + 2 O2 CO2 + 2 H2Ob. C6H12O6 + 6 O2 6 CO2 + 6 H2Oc. 2 C4H10 + 13 O2 8 CO2 + 5 H2Od. C7H16 + 11 O2 7 CO2 + 8 H2O
D. Single Replacement1. Definition - atoms of one element replace the atoms of another element that is part of a
compound. In other words, an element + a compound yields a new element + a new compounda. If the atom of the single element is a metal, it replaces the metal in the compound
(**metals can also replace hydrogen)b. If the atom of the single element is a non-metal, it replaces the non-metal in the
compound
2. General Form:AX + B BX + A or AX + Y AY + Xwhere A, B are metals or hydrogen and X, Y are non-metals
3. Examplesa. Cu + AgNO3 Cu(NO3)2 + Agb. K + H+(OH-) KOH + H2
c. Zn + HCl ZnCl2 + H2 d. NaI + Cl2 NaCl + I2
e. KBr + F2 KF + Br2
4. Do these reactions occur?a. Zn + H2SO4 H2 + ZnSO4 (yes, Zn is more reactive than H)b. Sn + 2 HNaNO3 Sn(NO3)2 + 2 Na (no, Sn is less reactive than Na)c. 2 NaCl + F2 2 NaF + Cl2 (yes, F is more reactive than Cl)d. CaCl2 + I2 CaI2 + Cl2 (no, I is less reactive than Cl)
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E. Double Replacement1. Definition - an exchange of cations (+ ions) between two ionic compounds
2. General Form:AB + CD AD + CB
(***remember, these are ionic compounds and the cations (metals) must be written first. A and C are the cations)
4. The “driving forces” in double replacement reactions (one of these three things must be a product in order for these reactions to occur):
a. a liquid (like water) must form, orb. a solid (a precipitate) must form, orc. a gas must form
5. What is a precipitate?a. It is insoluble or slightly soluble in waterb. A solubility chart can help determine thisc. Are these soluble or insoluble?
(1) BaCl2 - soluble, so the reaction will not occur(2) AgCl - insoluble, so the reaction will occur(3) Ca3(PO4)2 - insoluble, so the reaction will occur(4) NaNO3 - soluble, so the reaction will not occur
6. Do these reactions occur?a. FeS (s) + HCl (aq) FeCl2 (aq) + H2S (g) ( yes, a gas is produced)b. Pb(NO3)2 (aq) + 2 KI (aq) 2 KNO3 (aq) + PbI2 (s) (yes, PbI2 is insoluble and thus a
precipitate)c. FeCl3 (aq) + Al(NO3)3 (aq) Fe(NO3)3 (aq) + AlCl3 (aq) (no, both products are
soluble, no other “driving force” is present)d. H2SO4 (aq) + 2 KOH (aq) K2SO4 (aq) + 2 H+(OH-) (l)
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SYNTHESIS, DECOMPOSITION AND COMBUSTION REACTIONS
Synthesis:
Decomposition:
Combustion of a hydrocarbon:
Practice:
Balance each reaction below. Then identify the reaction type.
a. H2 + Br2 HBr ________________________
b. C4H8 + O2 CO2 + H2O ________________________
c. NaOH Na2O + H2O ________________________
d. Ba(ClO3)2 BaCl2 + O2 ________________________
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First write and balance the equation. Then identify the reaction type.
e. phosphorus + oxygen tetraphosphorus decoxide ________________________
f. pentane (C5H12) + oxygen carbon dioxide + water ________________________
g. magnesium chlorate magnesium chloride + oxygen ________________________
h. when solid calcium carbonate is heated calcium oxide and carbon dioxide are formed
________________________
i. the formation of calcium nitride from calcium and nitrogen________________________
j. sulfur trioxide mixes with water in the atmosphere to form sulfuric acid________________________
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SINGLE DISPLACEMENT REACTIONS ANDDOUBLE DISPLACEMENT REACTIONS
1. Single Displacement Reactions (aqueous ONLY)metals:
standard:
example:
metal + acid:standard:
example:
metal + water:standard:
example:
halogens:standard:
example:
2. Double Displacement (aqueous only)standard:
example:
3. Identify the reaction type for each reaction below. Then complete and balance the reaction.
__________________________a. Ba + AgNO3 ___________________________
__________________________b. F2 + KI ______________________________
11. Copper metal is put into a solution of silver nitrate. Solid silver precipitates, and copper (II) nitrate solution is formed.
___________________________
12. Methane gas burns in pure oxygen to give carbon dioxide and water
___________________________
13. When sodium carbonate is heated, it breaks down to form sodium oxide and carbon dioxide.
___________________________
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HOMEWORK – PRACTICE REACTION WRITING
Identify the reaction type (synthesis, decomposition, combustion, single displacement, double displacement) for each reaction written below. Then write the balanced equation for each reaction.
_______________________ 1. Magnesium is placed in a solution of aluminum nitrate
_______________________ 2. Calcium burns in pure oxygen
________________________ 3. The combustion of propane (C3H8)