Classifying Chemical Reactions

Types of Chemical Reactions Types of Chemical Reactions Do atoms rearrange in predictable patterns during chemical reactions? Why? Recognizing patterns allows us to predict future behavior. Weather experts use patterns to predict dangerous storms so people can get their families to safety. Political analysts use patterns to predict election outcomes. Similarly, chemists classify chemical equations according to their patterns to help predict products of unknown but similar chemical reactions. Model 1 – Types of Reactions Set A - Synthesis Set B - Decomposition 4Fe(s) + 3O2(g) → 2Fe2O3(s) MgCO3(s) → MgO(s) + CO2(g) N2(g) + 3H2(g) → 2NH3(g) 8Li2S(s) → 16Li(s) + S8(s) 2SO2(g) + O2(g) → 2SO3(g) 2H2O(l) → 2H2(g) + O2(g) MgO(s)+ H2O(l) → Mg(OH)2(aq) 2KClO3(s) → 2KCl(s) + 3O2(g) P2O5(g) + 3H2O(l) → 2H3PO4(aq) O2(g) 2Na2O2(s) → 2Na2O(s) + SO3(g) + H2O(l) → H2SO4(aq) H2O(l) + CO2(g) (NH4)2CO3(s) → 2NH3(g) + Set C - Single Replacement Set D - Double Replacement 2FeCl3(aq) + 3Zn(s) → 2Fe(s) + 3ZnCl2(aq) NaNO3(aq) AgNO3(aq) + NaCl(aq) → AgCl(s) + 2Al(NO3)3(aq) + 3Ca(s) → 3Ca(NO3)2(aq) + 2Al(s) →Mg(NO3)2(aq) + 2H2O(l) 2HNO3(aq) + Mg(OH)2(aq) Mg(s) + CuSO4(aq) → MgSO4(aq) + Cu(s) 3KBr(aq) FeBr3(aq) + K3PO4(aq) → FePO4(s) + 2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g) 2NaCl(aq) Na2CO3(aq) + CaCl2(aq) →CaCO3(s) + Cl2(g) + 2NaBr(aq) → 2NaCl(aq) + Br2(l) FeS(s) + 2HCl(aq) → H S(g) + FeCl (aq) ZnBr2(aq) + F2(g) → ZnF2(aq) + Br2(l) NaCl(aq) HCl(aq) + NaOH(aq) → H O(l) + 1. The chemical equations in Model 1 contain the phase notations (s), (l), (g), and (aq). Write each symbol by each meaning. dissolved in water liquid solid (aq) (l) (s) gas (g) 2. Based on the examples provided, which set(s) of reactions in Model 1 typically involve ions in solution (A, B, C or D)? C, D 3. Based on the examples provided, which set(s) of reactions in Model 1 typically involve gases and/or solids? A, B 4. Match each description below to one of the reactions sets (A, B, C or D) from Model 1. _____D_____ Ionic compounds dissolved in water switch partners. _____B_____ One compound breaks into elements or smaller compounds. _____A_____ Two or more elements or compounds combine to form one product. _____C_____ Part of an ionic compound is removed and replaced by a new element. 5. Define the following terms as they are commonly used in the English language. Synthesis — put together Decomposition — break down Single Replacement — one replaces another Double Replacement — two switch Combustion — burn 6. The four sets of chemical reactions shown in Model 1 have the following general names. Discuss within your group which name belongs to which set of chemical reactions. Write the name in the appropriate place in Model 1. Single Replacement Reaction C Double Replacement Reaction D Synthesis Reaction A Decomposition Reaction B 7. Can two elements be used as reactants for a synthesis reactions? If yes, give at least one example from Model 1 to support your answer. Yes, 4Fe(s) + 3O2(g) → 2Fe2O3(s) 8. Can two compounds be used as reactants for a synthesis reaction? If yes, give at least one example from Model 1 to support your answer. Yes, P2O5(g) + 3H2O(l) → 2H3PO4(aq) 9. What types of substances (elements or compounds) are seen in the products of decomposition reactions? Use examples from Model 1 to support your answer. Both elements and compounds can be seen in the products. MgCO3(s) → MgO(s) + CO2(g) and 8Li2S(s) → 16Li(s) + S8(s) 10. In single replacement reactions, do any of the atoms change their charge? If yes, use an example from Model 1 to describe the changes that take place. Yes, 2FeCl3(aq) + 3Zn(s) → 2Fe(s) + 3ZnCl2(aq) Iron changes from +3 to 0 and Zinc changes from 0 to +2 11. In double replacement reactions, do any of the atoms change their charge? If yes, use an example from Model 1 to describe the changes that take place. No 12. Choose one example from the set of synthesis reactions in Model 1. a. Write the chemical reaction in reverse. 2NH3(g) → N2(g) + 3H2(g) b. Label the reaction written in part a with one of the reaction types in Model 1. Decomposition 13. Identify each of the reactions below as synthesis (S), decomposition (D), single replacement (SR) or double replacement (DR). ____S_________ K2O(s) + H2O(l) → 2KOH(aq) ____DR________ 2MgCl2(aq) + Na2CO3(aq) → 2NaCl(aq) + MgCO3(s) ____D_________ 2Al2O3(s) → 4Al(s) + 3O2(g) ____SR________ Cu(NO3)2(aq) + Zn(s) → Cu(s) + Zn(NO3)2(aq) ____DR________ H2SO4(aq) + 2NaOH(aq) → Na2SO4(aq) + 2H2O(l) ____SR________ 2K(s) + 2H2O(l) → 2KOH(aq) + H2(g) ____S_________ 2O2(g) + N2(g) → N2O4(g) ____D_________ 2NaF(s) → 2Na(s) + F2(g) 14. A student writes the following incorrect chemical equation for the synthesis of magnesium Oxide. Mg + O2 → MgO2 Another student writes the following incorrect synthesis reaction. Mg + O → MgO a. What is the correct formula for magnesium oxide? Hint: Magnesium oxide is an ionic compound. MgO b. What is the correct formula for elemental oxygen? O2 c. Describe the error made by the first student. The student used the subscript from O2 in the product but only one O is needed for magnesium oxide. d. Describe the error made by the second student. Knowing only one oxygen is needed in magnesium oxide, the student disregarded the correct formula for elemental oxygen. e. Write the correct balanced chemical equation for the synthesis of magnesium oxide. 2Mg + O2 → 2MgO 15. A student writes the following incorrect chemical equation for a single replacement reaction between lithium bromide and fluorine. 2LiBr(aq) + F2(g) → 2Li(s) + 2FBr(g) a. In a single replacement reaction, part of an ionic compound is removed and replaced by a new element. What element will fluorine replace in lithium bromide? Hint: What is the most common ionic form of fluorine? Fluorine will replace the bromide ion in lithium bromide. b. What is wrong with the student’s prediction of the products in the above reaction? The compound FBr is not an ionic compound and is not likely to form in a single replacement reaction. c. Predict the products and write the correct balanced equation for the single replacement reaction between lithium bromide and fluorine. 2LiBr(aq) + F2(g) → Br2(g) + 2LiF(aq) 16. A student writes the following incorrect chemical equation for a double replacement reaction between iron(III) bromide and sodium hydroxide solutions. FeBr3(aq) + NaOH(aq) → FeOH(s) + NaBr3(aq) a. What is wrong with the chemical formula(s) of the product(s) predicted by this student? The iron ion would bond with three hydroxide ions. Only one bromide ion is needed to bond with sodium. b. Write the correct equation for the double replacement reaction between iron(III) bromide and sodium hydroxide. FeBr3(aq) + 3NaOH(aq) → Fe(OH)3(s) + 3NaBr(aq) 17. Consider the following chemical reaction written as a word equation. diphosphorus pentoxide + water → phosphoric acid a. Identify the type of chemical reaction from Model 1 that would describe this reaction. Synthesis b. Write chemical formulas under the names of the substances in the word equation. P2O5 + 3H2O → H3PO4 c. Balance the chemical equation. P2O5 + 3H2O → H3PO4 18. Use your understanding of common chemical reactions to predict the products for the following reactions. Writing a word equation may be helpful. Balance the chemical equations after you have written the correct chemical formulas for all of the reactants and products. a. b. c. d. e. f. 4Al(s) + 3N2(g) → 2Al2N3 (s) 2dinitrogen oxide(g) → 2N2(g) + O2(g) SrCl2(aq) + 2AgNO3(aq) → 2AgCl(s) + Sr(NO3)2(aq) 2chromium(III) nitrate(aq) + 3zinc chloride(aq) →3Zn(NO3)2 (aq) + 2CrCl3 (s) 2Na(s) + Cl2(g) → 2NaCl(s) Zn(s) + 2HCl(aq) → ZnCl2 + H2 Extension Questions Model 2 – Combustion Reactions 2C8H18(g) + 25O2(g) → 16CO2(g) + 18H2O(g) (C8H18 = octane—gasoline component) 2C4H10(g) + 13O2(g) → 8CO2(g) + 10H2O(g) CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) (C4H10 = butane—lighter fuel) (CH4 = methane—natural gas) 19. What are the products in all of the combustion reactions in Model 2? CO2(g) + H2O(g) 20. What reactant is common in all of the combustion reactions in Model 2? Hydrocarbon + O2(g) 21. The “fuel” in most combustion reactions is a hydrocarbon. Using the examples in Model 2, write a description for the classification of substances known as hydrocarbons. Hydrocarbons contain C and H and sometimes O 22. Predict the products of the following combustion reactions, and balance each reaction equation. a. C5H12 + 8O2 → 5CO2(g) + 6H2O(g) b. 2C2H2 + 5O2 → 4CO2(g) + 2H2O(g) 23. Compounds such as isopropyl alcohol (C3H7OH) and glucose (C6H12O6) can also undergo combustion in a similar way. Predict the products of the following combustion reactions, and balance each reaction equation. a. 2C3H7OH + 9O2 → 6CO2(g) + 8H2O(g) b. C6H12O6 + 6O2 → 6CO2(g) + 6H2O(g) 24. For each of the reaction types in Model 1, explain why a combustion reaction CANNOT be classified as that type. Use a complete sentence in each answer. All combustion reactions contain a hydrocarbon combining with oxygen producing water and carbon dioxide.