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Chemical Equations Name: __________________________________________Period: _____Date:_________ Part I: Parts and Meaning of a Chemical Equation: 1) _____________________________________= process by which one or more substances are changed into one or more different substances (atoms are rearranged) a) _____________________= original substances(written to the left of the arrow in a chemical equation) b) ________________________ = resulting substances(written to the right of the arrow in a chemical equation) ________ _____ _ CH4 + 2O2 _________ _ CO2 + 2H2O c) Indications of a chemical reaction (chemical change): • evolution of ____________ and/or ___________ • production of a ____________ (often seen as bubbles) • __________________________ • formation of a _________________________when two solutions are mixed (Precipitate = a solid that separates from a solution) d) __________________________ = a substance that speeds up a chemical reaction but is not permanently consumed in the reaction. • Catalysts DO NOT appear as reactants or products! • Ex: manganese dioxide is a catalyst in the following reaction: o 2H2O2 MnO2 O2 + 2H2O 1 A. Writing a Chemical Equation: 1) __________________________= a representation of the reactants and products in a chemical reaction a) ___________________________________ = a chemical equation in which the reactants and products in a chemical reaction are represented by words • Ex: sodium + water → sodium hydroxide + hydrogen __________________ __________________ b) _________________________________ = a chemical equation in which the reactants and products in a chemical reaction are represented by chemical symbols or chemical formulas • Ex: Na + H2O → NaOH + H2 reactants products c) ________________________ = whole number that appears to the right and below a chemical symbol in a chemical formula (if no number is written it is assumed to be “1”) • Indicates the number of ________________ or ______________________ • Ex: H2O subscript subscript (assumed to be “1”) d) __________________________ = whole number that appears in front of a reactant or product in a balanced chemical equation (if no number is written it is assumed to be “1”) • Indicates the number of molecules or moles • Ex: 2 CO2 coefficient • Ex: Al2S3 coefficient (assumed to be “1”) 2 e) ______________________________________________________= a formula equation where coefficients are added so equal numbers of each type of atom (ion) are represented on each side of the equation • Ex: 2 Na (s) + 2 H2O (l) → 2 NaOH (aq) reactants + H2 (g) products • _____ molecules of solid sodium reacts with _____ molecules of water to yield ___ • molecules of aqueous sodium hydroxide and _____ molecule of hydrogen gas. OR _____ moles of solid sodium reacts with ____ moles of water to yield ___ moles of aqueous sodium hydroxide and ____ mole of hydrogen gas. 2) In the chemical equation below, identify the reactants, products, subscripts, and coefficients 4 Fe + 3 O2 → 2 Fe2O3 • What are the reactant(s)?= ___________________________ • What are the product(s)? = _____________________________ • # of moles of O2 =__________________ • # of molecules of O2=_______________ • # of atoms of Fe in 2 Fe2O3 = _______________ • # of atoms of O in 3 O2 =_____________ 3 3) Symbols you may see in a chemical equation: Symbol Meaning “yields”; indicates result of a reaction Indicates a reversible reaction A reactant or product in the solid state Alternative to (s); used only for a precipitate (solid) falling out of solution A reactant or product in the liquid state A reactant or product in aqueous solution (dissolved in water) A reactant or product in the gaseous state Alternative to (g); used only for a gaseous product Reactants are heated Pressure at which the reaction is carried out, in this case 2 Temperature at which reaction is carried out, in this case O°C A catalyst is used to speed up the reaction rate, in this case MnO2 would be used to speed up the reaction rate. Part II: Requirements for Chemical Equations: 1) The equation must represent the known facts with all reactants and products identified. 2) The equation must contain the correct formulas of the reactants and products. 3) A chemical reaction obeys the “Law of Conservation of Matter” • ____________________________________________________ = matter cannot be either created or destroyed in ordinary chemical or physical means. 4) Why do we balance equations? • The ________________________________________________________must not be violated! • This means you must balance equations. (Equations are balanced by adding _____________________________________, NOT subscripts.) 4 5) Atomic theory can be used to explain why chemical reactions obey the “Law of Conservation of Matter”. • _________ atoms present at the start of a chemical reaction are present at the end of that chemical reaction (atoms are simply rearranged during a chemical reaction). • Since no atoms are created or destroyed in a chemical reaction no matter is created or destroyed in a chemical reaction. • Since no matter is created or destroyed in the chemical reaction the mass of the reactants must equal the mass of the products in a chemical reaction. 6) A _____________________ chemical equation details how a chemical reaction obeys the “Law of Conservation of Matter”. Part III: Information a Chemical Equation Does NOT Supply: 1) Whether the reaction will actually____________. Chemical equations can be written for reactions that do not necessarily take place. 2) The __________of a reaction. 3) The _____________________atoms or ions take in moving from reactants to products. Part IV: Balancing Equations 1) Write a word equation 2) Write a formula equation a) remember naturally occurring ___________________ molecules: • __________________________________ b) unless otherwise noted, other elements are represented by the element symbol; ex: magnesium = Mg • Ex: 2 Mg + O2 2MgO c) remember the formulas for acids: • HCl = Hydrochloric Acid • H2CO3 = Carbonic Acid • HNO3 = Nitric Acid • H2SO4 = Sulfuric Acid • H3PO4 = Phosphoric Acid • CH3COOH = Acetic Acid(NOTE: the positive ion (H+) is at the end) d) remember the rules for writing formulas for ionic compounds (________) • Metals and Nonmetals! e) remember the rules for writing formulas for molecular compounds (______________) • Only NONMETALS! f) remember the formula for water, ________ • HOH = hydrogen hydroxide 5 3) Write a balanced chemical equation by adding_____________________, NOT subscripts (this will require trial and error, the following guidelines may be helpful) a) balance the different types of atoms ________________ b) first, balance the atoms of elements that are combined and that appear only ___________on each side of the equation c) balance ____________________________that appear on both sides of the equation as single units d) balance H atoms and O atoms after atoms of all other elements have been balanced 4) Conduct an atom inventory throughout the process. a. _________________________________________ (for a chemical equation) = a “bookkeeping” technique designed to count the number of each type of atom (ion) represented on each side of a chemical equation. 5) Be certain that the coefficients represent the ______________________________possible whole number ratio of reactants and products. Ex: 4 K + 2 Cl2 4 KCl (All coefficients can be reduced!) 2 K + 1 Cl2 2 KCl (Correct! -Shows reduction) 6) Common problems when balancing equations: a) You must write correct formulas! b) Once a correct formula is written, _____________________CANNOT be changed! c) Don’t forget about the naturally occurring ________________________________ molecules: H2, O2, N2, Cl2, Br2, I2, F2 7) For each of the following, write a formula equation and a balanced chemical equation. a) Hydrogen reacts with oxygen to produce water. b) Zinc reacts with hydrochloric acid to produce a solution of zinc chloride and hydrogen gas. c) Aluminum sulfate reacts with calcium hydroxide to form aluminum hydroxide and calcium sulfate. d) Nitrogen reacts with hydrogen to form ammonia (NH3) 6 Chemical Equations Worksheet 1) Which side of the yields arrow do you find reactants? ______________________________ 2) Which side of the yields arrow do you find products? _______________________________ 3) In a chemical equation, what do the coefficients represent? ______________________________ 4) In a chemical equation, what do the subscripts represent? ______________________________ 5) How many atoms of chlorine are present in 2AlCl3 =__________________ 6) How many moles of aluminum chloride are present in 2AlCl3 =__________________ 7) How many atoms of aluminum are present in 2AlCl3 =__________________ 8) How many molecules of aluminum chloride are present in 2AlCl3 =_____________ 9) Why do we balance chemical equations? 10) What do the following symbols represent when used in a chemical equation? a) H2 = _________________________________________________________________________ b) Ca(OH)2 = _____________________________________________________________________ c) MgSO4 (s) = _____________________________________________________________________ d) O2 (g) = ________________________________________________________________________ e) H2O (l) = ________________________________________________________________________ f) NaCl (aq) = ______________________________________________________________________ g) NaCl (l) = _______________________________________________________________________ 11) What do the following symbols involving the yields arrow indicate? ∆ a) 2Mg + O2 2MgO __________________________________________________________ b) 2H2 + O2 2H2O ____________________________________________________________ c) C3H6 + H2 80°C C3H8 ____________________________________________________________ d) N2 + 3H2 Fe 2NH3 ___________________________________________________________________________________________ 12) List the naturally occurring diatomic molecules. _______________________________________________ 13) Balance the following chemical equations. a) ___ P4 + ___ O2 ___ P2O3 b) ___ Na3PO4 + ___ KOH ___ NaOH + ___ K3PO4 c) ___ MgF2 + ___ Li2CO3 ___ MgCO3 + ___ LiF 7 Practice Balancing Equations For each of the following, write a formula equation and balance the equation. If no additional coefficients are needed, write “balanced”. Don’t forget about the diatomic molecules! 1. zinc + silver nitrate zinc nitrate + silver 2. barium chloride + sodium sulfate 3. copper + nitrogen barium sulfate + sodium chloride copper (II) nitride 4. magnesium + sulfuric acid magnesium sulfate + hydrogen 5. barium nitrate + ammonium chloride 6. potassium + water barium chloride + ammonium nitrate potassium hydroxide + hydrogen 7. fluorine + aluminum oxide 8. lithium + phosphoric acid aluminum fluoride + oxygen lithium phosphate + hydrogen 8 9. aluminum + hydrochloric acid 10. nickel + nitric acid aluminum chloride + hydrogen nickel(II) nitrate + hydrogen 11. sodium chloride + lead(II) nitrate 12. magnesium + chlorine 13. iron + oxygen magnesium chloride iron(III) oxide 14. water + magnesium nitrate 15. sodium oxide + water 16. iron + copper(II) nitrate 17. calcium + water lead(II) chloride + sodium nitrate magnesium oxide + nitric acid sodium hydroxide iron(II) nitrate + copper calcium hydroxide + hydrogen 9 18. chlorine + lithium iodide 19. aluminum oxide lithium chloride + iodine aluminum + oxygen 20. carbon + iron(III) oxide 21. aluminum + zinc chloride iron + carbon dioxide aluminum chloride + zinc 22. mercury(II) sulfide + calcium oxide 23. bromine + water + sulfur dioxide calcium sulfide + mercury(II) oxide hydrogen bromide + sulfuric acid 24. diphosphorus pentaoxide + barium oxide 25. silver acetate + sodium phosphate 26. tin + potassium hydroxide barium phosphate silver phosphate + sodium acetate potassium tin(II) oxide (K2SnO2) + hydrogen 10 Part V: Types of Reactions & Predicting Products: 1. ____________________: (S) • 2 or more substances (A and B) react to produce a SINGLE product (AB) • General format: A + B AB Ex: NH3 + HCl 2 Na + C12 NH4Cl 2 NaCl Synthesis Practice: For each of the following, predict the products and write a word equation. Next, write a formula equation and a balanced chemical equation. Finally, write the type of reaction represented by each chemical equation. a) magnesium + oxygen → b) sodium + fluorine → c) magnesium + fluorine → d) lithium + chlorine → e) barium + oxygen → f) potassium + oxygen → 11 2. __________________________________: (D) – the opposite of synthesis • A SINGLE compound breaks up or decomposes into simpler substances • General format: AB A + B Ex: H2CO3 H2O + CO2 2 Al2O3 4 Al + 3 O2 Decomposition Practice: For each of the following, predict the products and write a word equation. Next, write a formula equation and a balanced chemical equation. Finally, write the type of reaction represented by each chemical equation. a) water → b) mercury(II) oxide → c) magnesium chloride → d) silver oxide → 12 3. _________________________________________________: (SD) • Element (A) + compound (BC) yields new compound (AC) + a new element (B) • One element replaces another element in a compound • General format: A + BC AC + B Ex: Cl2 + 2 KBr 2 KCl + Br2 2 Na + 2 H2O 2 NaOH + H2 Single Displacement Practice: For each of the following, predict the products and write a word equation. Next, write a formula equation and a balanced chemical equation. Finally, write the type of reaction represented by each chemical equation. a) aluminum + lead(II) nitrate → b) lithium + water → c) aluminum + sulfuric acid → d) chlorine + potassium bromide → e) aluminum + silver nitrate → f) barium + water → g) lithium + hydrochloric acid → 13 4. ____________________________________________________: (DD) • Positive and negative ions are exchanged • General format: AB + CD CB + AD Ex: Ba(OH)2 + H2SO4 BaSO4 + 2 H2O AgNO3 + NaCl AgCl + NaNO3 Double Displacement Practice: For each of the following, predict the products and write a word equation. Next, write a formula equation and a balanced chemical equation. Finally, write the type of reaction represented by each chemical equation. a) potassium iodide + lead(II) nitrate → b) acetic acid + sodium hydroxide → c) nitric acid + potassium hydroxide d) sulfuric acid + potassium hydroxide e) calcium phosphate + acetic acid f) Identify the following types of chemical reactions (S, D, SD, DD): __________________ 1) 2 H2O2 2 H2O +O2 __________________ 2) 4 Fe + 3 02 __________________ 3) Cl2 + 2 NaBr 2 NaCl + Br2 __________________ 4) Zn + H2SO4 ZnSO4 + H2 __________________ 5) Pb(NO3)2 + K2CrO4 2 Fe2O3 PbCrO4 + KNO3 14 Predicting Products of Chemical Reactions SUMMARY TYPE OF REACTION REACTANTS PRODUCTS GENERIC EQUATION Synthesis (S) 2 or more substances ONE compound Decomposition (D) ONE compound 2 or more elements and/or compounds Single Displacement (SD) Element + Compound New compound & new element A + BC Double Displacement (DD) Compound + Compound 2 new compounds AB + CD A +B AB AB A + B AC + B AD + CB Identify the following types of reactions & explain why for the first 4 questions. 1) 2 H2O2 MnO 2 2 H2O + O2 _______________________ a) Why? 2) Cu + 2 AgNO3 → 2 Ag + Cu(NO3)2 __________________________________ a) Why? 3) 4 Al + 3 S → 2 Al2S3 _______________________ a) Why? 4) Zn(NO3)2 + Na2CrO4 → ZnCrO4 + 2 NaNO3 _______________________ a) Why? 5) F2 + 2 LiBr → 2 LiF + Br2 _______________________ 6) NH4NO3 → N2O + 2 H2O __________________________________ 7) 2 SO2 + O2 → 2 SO3 __________________________________ 8) BaO + H2O → Ba(OH)2 _______________________ 9) Mg + H2SO3 → MgSO3 + H2 _______________________ 10) 3 CuBr2 + Al2O3 → 3 CuO + 2 AlBr3 __________________________ 15 Part VI: Reaction Rates 1) _____________________________ = the rate (speed) of disappearance of a reactant or the rate of appearance of a product in a chemical reaction a) A chemical reaction that takes a long time to happen has a slow reaction rate. b) A chemical reaction that takes a short time to happen has a fast reaction rate. A. Factors Affecting Reaction Rate 1) ______________________________________ a) Reactions occur at different rates depending on the reactants. b) Some reactions occur almost instantaneously (such as double-replacement reactions). c) Other reactions occur slower. 2) __________________________________ = a measure of the number of particles of matter per unit volume a) An increase in the concentration of the reactants generally increases reaction rate. b) A decrease in the concentration of the reactants generally decreases reaction rate. 3) __________________________________ = a measure of the average kinetic energy of the particles in a sample of matter a) An increase in temperature increases reaction rate. b) A decrease in temperature decreases reaction rate. 4) Presence of a __________________________= a substance that increases the rate of a chemical reaction without being permanently changed a) A catalyst will increase reaction rate. b) A catalyst is __________ permanently changed in a chemical reaction. B. Collision Theory 1) Assumptions of collision theory: a) Reacting molecules must ____________ with each other. b) Reacting molecules must collide with sufficient ______________. c) Reacting molecules must collide in an orientation that can lead to ________________________ of the atoms. 16 2) Use collision theory to explain why an increase in CONCENTRATION increases reaction rate: a) At a _______________ concentration ____________ reactant molecules are present. b) When more reactant molecules are present more frequent __________________ occur. c) When more frequent collisions occur there are more chances for molecules to react (so reactions happen ___________________). 3) Use collision theory to explain why an increase in TEMPERATURE increases reaction rate: a) Molecules with a higher kinetic energy move faster, collide more often, and have more energetic collisions. b) A higher temperature means that the average kinetic energy of the reacting molecules is _____________________; at a higher temperature there are more molecules with a higher kinetic energy. c) At a higher temperature there are____________________________________________ giving molecules more chances to react (so reactions happen faster). d) At a higher temperature, more molecules possess enough kinetic energy to react so a higher percentage of collisions result in molecules reacting (so reactions happen faster). 17 Practice Predicting Products, Balancing Equations, and Types of Reactions For each of the following, predict the products and write a word equation. Next, write a formula equation and a balanced chemical equation. Finally, write the type of reaction represented by each chemical equation on the line next to the number. ____1. zinc + sulfur ____2. potassium + water ____3. calcium + nitric acid ____4. silver oxide ____5. hydrochloric acid + sodium hydroxide ____6. sodium sulfate + calcium nitrate ____7. zinc chloride + ammonium oxide 18 ____8. zinc + copper(II) acetate ____9. sodium + sulfuric acid ____10. calcium + water ____11. sulfuric acid + potassium hydroxide ____12. chlorine + potassium bromide ____13. zinc + hydrochloric acid ____14. aluminum + iron(III) oxide 19 ____15. copper (II) acetate + potassium permanganate ____16. calcium peroxide ____17. copper (II) sulfide + barium iodide ____18. iron (III) nitrate + sodium hydroxide ____19. nitric acid + aluminum hydroxide ____20. sodium + oxygen ____21. lithium + hydrochloric acid ____22. potassium nitrate + zinc peroxide 20 Review Worksheet: Answer the questions 1-8, using this equation: 2 Na (s) + 2 H2O (l) 2 NaOH (aq) + H2 1. What are the reactant(s)? _____________________ 2. What are the product(s)? _______________________ 3. How many molecules of H2 are present as a product? ___________ 4. How many moles of NaOH are present? ____________ 5. How many atoms of H are present in 2 H2O? __________ 6. What molecule or compound is a gas? __________________ 7. What element or compound was dissolved in water? _________________ 8. What element or compound is a solid? _________________ 9. Why do we balance equations? 10. How do you correctly notate that heat is needed in the following equation, in order to produce the product? 2 Cu + O2 2 CuO 11. List the diatomic molecules. _____________________________________________________________ 12. What is a catalyst? 13. Write the formulas for the following acids: a) Carbonic Acid = ______________________________ b) Nitric Acid = ______________________________ c) Sulfuric Acid = ______________________________ d) Phosphoric Acid = ______________________________ e) Hydrochloric Acid = ______________________________ f) Acetic Acid = ______________________________ 21 14. List the 4 indicators that a chemical reaction occurred. 15. What is a reaction rate? 16. What are four factors that affect the reaction rate? 17. Using collision theory, EXPLAIN why increasing the concentration, increases the reaction rate? 18. Using collision theory, EXPLAIN why increasing the temperature, increases the reaction rate? _______ 19. chlorine + potassium iodide _______ 20. magnesium hydroxide + hydrochloric acid _______ 21. zinc + potassium dichromate _______ 22. potassium + chlorine ‘ _______ 23. mercury(II) oxide _______ 24. copper(II) sulfate + zinc 22 Unit Learning Map (10 days): Chemical Reactions/Equations Mrs. Hostetter Class: Chemistry B – PA standard: Describe factors that influence the frequency of collisions during chemical reactions that might affect the reaction rates. Instructional Tools: Unit Essential Question(s): Guided Notes Lab Materials: Models of Chemical Reactions Chemical Reactions and What are chemical reactions and how are they represented? Concept: Writing Word Equations, Formula Equations, and Balanced Chemical Equations Lesson Essential Question(s): 1) How is a chemical reaction represented? 2) Given a description of a chemical reaction, how are a word equation and a formula equation written? 3) How is a formula equation balanced by trial and error? Vocabulary: Chemical reaction (chemical change) Reactant Product Indications of a chemical reaction Chemical symbol Chemical formula Chemical equation Word equation Formula equation Atom inventory Subscript Coefficient Balanced chemical equation Concept: Balanced Chemical Equations Lesson Essential Question(s): 1) 2) 3) How can atomic theory be used to explain why chemical reactions obey the “Law of Conservation of Matter”? How are balanced chemical equations translated into sentences? What information is given/not given by a balanced chemical equation? Vocabulary: Law of conservation of Matter Atomic theory Atom Molecule Formula unit Catalyst Symbols in a chemical equation Chemical Equations Reaction Rates Chemistry Competition Concept: Types of Chemical Reactions and Predicting Products Lesson Essential Question(s): 1) How can synthesis, decomposition, singledisplacement, and double-displacement reactions be recognized and described? 2) Given the reactants, how can the products of simple chemical reactions be predicted? Vocabulary: Synthesis reaction Decomposition reaction Single-displacement reaction Double-displacement reaction Concept: Reaction Rates Lesson Essential Question(s): 1) 2) What effect do nature of reactants, concentration, temperature, and presence of a catalyst have on reaction rate? How can collision theory be used to explain why concentration and temperature affect reaction rate as they do? Vocabulary: Reaction rate Concentration Temperature Catalyst Collision theory 23 Chemical Equations Vocabulary: 1) Chemical reaction = process by which one or more substances are changed into one or more different substances (atoms are rearranged) 2) Reactants = original substances(written to the left of the arrow in a chemical equation) 3) Products = resulting substances(written to the right of the arrow in a chemical equation) 4) Indications of a chemical reaction (chemical change): evolution of heat and/or light; production of a gas (often seen as bubbles); color change; formation of a precipitate when two solutions are mixed 5) Precipitate = a solid that separates from a solution 6) Catalyst = a substance that speeds up a chemical reaction but is not permanently consumed in the reaction 7) Chemical equation = a representation of the reactants and products in a chemical reaction 8) Word equation = a chemical equation in which the reactants and products in a chemical reaction are represented by words 9) Formula equation = a chemical equation in which the reactants and products in a chemical reaction are represented by chemical symbols or chemical formulas 10) Atom inventory = a “bookkeeping” technique designed to count the number of each type of atom (ion) represented on each side of a chemical equation 11) Subscript = whole number that appears to the right and below a chemical symbol in a chemical 12) Coefficient = whole number that appears in front of a reactant or product in a balanced chemical equation (if no number is written it is assumed to be “1”) 13) Balanced chemical equation = a formula equation where coefficients are added so equal numbers of each type of atom (ion) are represented on each side of the equation 14) The Law of Conservation of Matter = matter cannot be either created or destroyed in ordinary chemical or physical means 15) Synthesis(S) = 2 or more substances combine to form a SINGLE product; General format: A + B → AB 16) Decomposition (D) = the opposite of synthesis; Single substance breaks up or decomposes into simpler substances; General format: AB → A + B 17) Single Displacement(SD) = One element replaces another element in a compound; General format: A + BC → AC + B 18) Double Displacement(DD) = Positive and negative ions are exchanged; General format: AB + CD → CB + AD 19) Reaction rate = the rate (speed) of disappearance of a reactant or the rate of appearance of a product in a chemical reaction 20) Concentration = a measure of the number of particles of matter per unit volume 21) Temperature = a measure of the average kinetic energy of the particles in a sample of matter 22) Assumptions of collision theory = a) Reacting molecules must collide with each other b) Reacting molecules must collide with sufficient energy c) Reacting molecules must collide in an orientation that can lead to rearrangement of the atoms 24