ANSWER KEY. Study Guide: Chemical Equations, Reactions, & Stoichiometry

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1 ANSWER KEY Study Guide: Chemical Equations, Reactions, & Stoichiometry Write a word equation and a formula equation for a given chemical equation. Balance chemical equations and apply the use of state symbols (s), (l), (g) and (aq). Describe the relationship between the law of conservation of matter and balancing chemical equations. List observations that would indicate that a chemical reaction has taken place. Define and give general equations for synthesis, decomposition, single-displacement, and double displacement reactions. Classify reactions as synthesis, decomposition, single-displacement, double-displacement, or combustion reactions Predict products of simple reactions given the reactants. Use an activity series to predict whether a given reaction will occur and what the products will be. Describe the importance of the mole ratio in stoichiometric calculations Write a mole ratio relating two substances in a chemical equation. Use mole ratios to calculate the amount of reactants or products in a reaction (calculate moles and/or grams) given the mass or moles of a different reactant or product. Describe the rearrangements of atoms involved chemical reactions. Distinguish between spontaneous and nonspontaneous reactions. Distinguish between exothermic and endothermic reactions. To prepare for this test you should: Go over all past worksheets (especially the packet on types of reactions) Review/revise all of your notes for this topic Review/revise all quizzes from this topic (rework all problems missed) Do the practice problems below If needed: go back to resources on to get more help with topics PRACTICE QUESTIONS: 1. Write the formula equation for the following reactions. a. Hydrogen carbonate decomposes into water and carbon dioxide gas. H 2CO 3(aq) H 2O (l) + CO 2(g) b. Sulfur dioxide and water yields hydrogen sulfate SO 2(g) + H 2O (l) H 2SO 4(aq) c. Iron (II) sulfide plus hydrogen sulfate yields hydrogen sulfide and iron sulfate FeS + H 2SO 4(aq) H 2S + FeSO 4(aq) d. Beryllium fluoride plus magnesium metal yields magnesium fluoride and beryllium metal BeF 2 + Mg (s) MgF 2 + Be (s) e. Copper (II) chloride plus 2 moles of silver (I) nitrate yields 1 mole of copper nitrate and 2 moles of solid silver chloride

2 CuCl 2(aq) + 2AgNO 3(aq) Cu(NO 3) 2(aq) + 2AgCl (s) f. Dinitrogen trioxide plus water yields hydrogen nitrite N 2O 3 + H 2O (l) HNO 2(aq) 2. Write the word equation for the following reactions. a. Na2SO4(aq) + SrCl2(aq) 2NaCl(aq) + SrSO4(s) Sodium sulfate plus strontium chloride yields sodium chloride and strontium sulfate. b. N2O5 + H2O HNO3 Dinitrogen pentoxide reacts with water yielding hydrogen nitrate (nitric acid). c. SrBr2 + (NH4)2CO3 SrCO3 + NH4Br Strontium bromide plus ammonium carbonate strontium carbonate and ammonium bromide. d. BaO2 + H2SO4 BaSO4 + H2O2 Barium oxide plus hydrogen sulfate (sulfuric acid) yields barium sulfate and dihydrogen dioxide. e. K2O + H2O KOH Potassium oxide plus water yields potassium hydroxide f. Mg + N2 Mg3N2 Magnesium metal reacts with nitrogen gas forming magnesium nitride. 3. Balance the following equations, be sure to include appropriate state symbols. a. NH4NO3(aq) N2O(g) + 2H2O(l) b. Ca(OH)2(s) + CO2(g) CaCO3(s) + H2O(l) BALANCED c. 2H3PO4(aq) H4P2O7 + H2O(l) d. Na2CO3(aq) + 2HCl(aq) 2NaCl(aq) + H2O + CO2(g) e. 3AgNO3(aq) + FeCl3(aq) Fe(NO3)3(aq) + 2AgCl(aq) f. 3BaCl2(aq) + Al2(SO4)3(aq) 3BaSO4(s) + 2AlCl3(aq) g. 2Al(OH)3(s) + 3H2SO4(aq) Al2(SO4)3(aq) + 6H2O(l) h. Fe2(SO4)3(aq) + 6KOH(aq) 3K2SO4(aq) + 2Fe(OH)3(s) i. 2C2H2 + 5O2(g) 4CO2(g) + 2H2O(g) j. 2 (NH4)2Cr2O7 4NH3(l) + 2H2O(l) + 2Cr2O3(s) + 3O2(g) 4. Describe the relationship between the law of conservation of matter and balancing chemical equations. State the law of conservation of matter. What is the relationship between atoms and matter. What happens to the atoms in a chemical reaction? How do new compounds form? Do these compounds have the same properties as the original compounds/elements? Why/why not? How does this law related to

3 balancing chemical equations? What do you need to make sure happens when you balance equations? The words reactants and products should be included in your answer. 5. List 5 observations you would make in lab to tell that a chemical reaction had taken place. See notes and PPT on evidence of chemical reactions. 6. Define and give the general equation for the following types of reactions See notes and PPT on types of chemical reactions. a. Synthesis b. Decomposition c. Single displacement d. Double Displacement e. Combustion 7. Identify which type of chemical reaction is shown. Then predict the products and write the balanced chemical reaction including state symbols a. S8 + 12O2(g) 8SO3 Synthesis b. 2C7H O2(g) 14CO2(g) + 10H2O(g) Combustion c. 2NaOH(aq) + FeCl2(aq) 2NaCl(aq) + Fe(OH)2(s) Double Displacement d. 2K (s) + Br2(g) 2KBr(aq) Synthesis e. 3V2O5 + 10Al(s) 5Al2O3(s) + 6V(s) Single Displacement (NOTE: V is not on reactivity table so would be fair to state NO Reaction) f. MgCO3(s) MgO(s) + CO2(g) Decomposition g. 2Zn(s) + Fe(NO3)2(aq) 2ZnNO3(aq) + Fe(s) Single Displacement h. 2NaI(aq) + Cl2(g) 2NaCl(aq) + I2(g) Single Displacement i. CH3CH2OH + 3O2(g) 2CO2(g) + 3 H2O(g) Combustion j. AgCl(aq) + Au(s) No Reaction Single Displacement k. BeSO4 + 2NH4OH(aq) (NH4)2SO4(aq) + Be(OH)2 Double Displacement 8. Describe the importance of the mole ratio in a stoichiometric calculations. What is a mole ratio? What does it tell you about the compounds in the reaction? What is it used for in stoichiometry? (Specifically what does this step allow you to do in the problem?) 9. Write the mole ratios for the given equation C7H O2 7 CO2 + 8 H2O a. C7H16 : O2 1:11 b. CO2 : C7H16 7:1 c. O2 : H2O 11:8 d. CO2 : H2O 7:8 e. H2O : C7H16 8:1 f. O2 : CO2 11:7 10. Use dimensional analysis to solve the following problems. a. Using the following formula, determine the number of moles of sulfur trioxide formed if you start with 19.0 moles of oxygen gas. S8 + 12O2 8SO3

4 b. Using the following formula, determine how many grams of hydrochloric acid are needed to produce 150 grams of iron chloride. FeS + HCl FeCl2 + H2S c. Nitrogen gas reacts with hydrogen gas to produce ammonia (NH3). What mass of ammonia is produced if you use 140 moles of nitrogen gas? d. Carbon reacts with water to produce carbon monoxide and hydrogen gases. If the reaction generates 145 grams of carbon monoxide, how many grams of carbon did you start with? e. When 85 grams of tricarbon octahydride combusts, how many grams of carbon dioxide is released? f. In a synthesis reaction magnesium reacts with nitrogen to form magnesium nitride. How many grams of magnesium nitride are produced if you start with 45 grams of magnesium?

5 g. Ammonium sulfate reacts with calcium carbonate. How many moles of product are produced if you start with 670 grams of ammonium sulfate? 11. What happens to the atoms during a chemical reaction? Where do the atoms in the reactants go? How do new compounds form? Does the new compounds have the same properties as the original reactants? Why/why not? 12. What is the difference between a spontaneous and a non-spontaneous reaction? See notes be sure to include how energy is related. 13. What is the difference between an endothermic and an exothermic reaction? Give an example of each. See you notes. Define each term. How does this affect temperature? Give a specific chemical reaction that demonstrates each type of reaction. If you feel you need more practice than this than create your own problems and share/trade with a friend. STUDY HARD! Good Luck! Mrs. P