1. Chapter 10: Chemical Reactions

2. Chemical Reactions Defn – process by which the atoms of one or more substances are rearranged Defn – process by which the atoms of one or more substances are rearranged - new substances are formed

3. Evidences of a chemical reaction 1) gas production 2) light production 3) temperature change (endo/exothermic) 4) precipitate formed (solid from 2 liquids) 5) permanent color change

4. Energy is stored in compounds as chemical potential energy due to specific arrangements of atoms. A chemical reaction changes the potential energy present. When energy is lost as heat, it is called a __________________. These reactions get hotter. Sometimes energy is gained; heat is added for a reaction to occur. These are called ______________________, which get colder. Energy is stored in compounds as chemical potential energy due to specific arrangements of atoms. A chemical reaction changes the potential energy present. When energy is lost as heat, it is called a __________________. These reactions get hotter. Sometimes energy is gained; heat is added for a reaction to occur. These are called ______________________, which get colder. exothermic reaction endothermic reaction

5. Word Equation Defn – equation expressed in words Defn – equation expressed in words Iron + chlorine  iron (III) chloride

6. Formula Equation Defn – equation with chemical formulas Defn – equation with chemical formulas Coefficients – whole # placed in front of compound Coefficients – whole # placed in front of compound Balances the number of atoms Balances the number of atoms 2 Fe + 3 Cl 2  2 FeCl 3

7. Parts Of A Reaction Symbols Symbols (s) (l) (g) (aq) solid liquid gas aqueous (dissolved in water) Δ heat added

8. example Solid calcium carbonate reacts with a solution of hydrochloric acid to produce aqueous calcium chloride, gaseous carbon dioxide, and liquid water Solid calcium carbonate reacts with a solution of hydrochloric acid to produce aqueous calcium chloride, gaseous carbon dioxide, and liquid water CaCO 3 (s) + HCl (aq) CaCl 2 (aq) + CO 2 (g)+ H 2 O (l)

9. Diatomic Elements Defn – 7 elements that NEVER occur as singular atoms (always paired with an the same or different element) Defn – 7 elements that NEVER occur as singular atoms (always paired with an the same or different element) H2 O2 F2 Br2 I2 N2 Cl2 Ex: 2 HCl + K  2 KCl + H 2

10. Balancing Equations Number of reactant atoms on left of an element must equal number of product atoms on the right Number of reactant atoms on left of an element must equal number of product atoms on the right Must obey law of conservation of mass Must obey law of conservation of mass

11. Rules for balancing equations 1) Only coefficients are changed in balancing reactions 2) Never change subscript during balancing 3) Coefficients are placed in front of compound and multiplied across compound to get total # of atoms of each element

12. Helpful Hints Balance hydrogen and oxygen last Balance hydrogen and oxygen last Balance polyatomic ions as a group if present on both reactants and products Balance polyatomic ions as a group if present on both reactants and products

13. Before Before After After MgCl 2 + NaOH  Mg(OH) 2 + NaCl 1 Mg 2 Cl1 Cl 1 Na 1 OH2 OH MgCl 2 + 2 NaOH  Mg(OH) 2 + 2 NaCl 1 Mg 2 Cl 2 Na 2 (OH)

14. Sample Problems sodium and chlorine combine to form sodium chloride sodium and chlorine combine to form sodium chloride Na + Cl 2 NaCl122

15. Sample Problems sodium hydroxide and calcium bromide react to produce calcium hydroxide and sodium bromide sodium hydroxide and calcium bromide react to produce calcium hydroxide and sodium bromide NaOH CaBr 2 Ca(OH) 2 NaBr + +  2 2 1 1

16. Sample Problems aluminum sulfate and calcium hydroxide produce calcium sulfate and aluminum hydroxide aluminum sulfate and calcium hydroxide produce calcium sulfate and aluminum hydroxide Al 2 (SO 4 ) 3 Ca(OH) 2 CaSO 4 Al(OH) 3 + +  1 2 3 3

17. Classifying Chemical Reactions Synthesis Synthesis Decomposition Decomposition Single replacement Single replacement Double Replacement Double Replacement Combustion Combustion

18. Synthesis Defn – two or more substances react to form ONE product Defn – two or more substances react to form ONE product A + B  AB

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20. Synthesis reaction of two elements reaction of two elements ___ Al + ___ Cl 2  ___ AlCl 3 Al 3+ Cl 1- 223

21. reaction of two compounds reaction of two compounds reaction of element and compound reaction of element and compound Synthesis CaO + H 2 O  Ca(OH) 2 SO 2 + O 2  SO 322

22. Decomposition defn – one substance breaks down into two or more simpler products defn – one substance breaks down into two or more simpler products AB  A + B

23. Break yoself fool!

24. Decomposition Ex reaction Ex reaction __ NaN 3 (s)  ___ Na (s)+ ___ N 2 (g) 223 __ CaO (s)  ___ Ca (s)+ ___ O 2 (g) 221

25. Single Replacement Reactions Defn – one element replaces another element in a compound to form new compound Defn – one element replaces another element in a compound to form new compound A + BX  AX + B

26. I’m gon’ dance with yo’ lady

27. Reactivity Series metals metals halogens halogens Li K Ca Na Mg Al Mn Zn Fe Ni Sn Pb Cu Ag Au most active least active F Cl Br I most activeleast active

28. examples aluminum + iron (III) oxide aluminum + iron (III) oxide Al Fe 2 O 3 + Stronger? Al 3+ O 2- Al 2 O 3 Fe + Fe 3 + O 2- 2 211

29. examples silver + copper (I) nitrate silver + copper (I) nitrate Ag CuNO 3 + Stronger? Cu 1 + NO 3 1- NO RXN

30. examples fluorine gas + sodium bromide fluorine gas + sodium bromide F2F2 NaBr + Stronger? Br 2 NaF+ Na 1 + F 1- 2211

31. examples chlorine gas + hydrogen fluoride chlorine gas + hydrogen fluoride Cl 2 HF + Stronger? NO RXN

32. Double Replacement Defn – exchange of cations between two ionic compounds Defn – exchange of cations between two ionic compounds A B + C D  AD + CB switch

34. 3 possible products of double replacement rxns Precipitate Precipitate Gas Gas Water Water

35. Ex problem lithium iodide and aqueous silver nitrate react lithium iodide and aqueous silver nitrate react Li 1+ I 1- Ag 1+ NO 3 1- Li I AgNO 3 LiNO 3 Ag I (s) + +

36. Combustion defn – compound reacts with O 2 defn – compound reacts with O 2 Hydrocarbon – cmpd w/ only carbon and hydrogen Hydrocarbon – cmpd w/ only carbon and hydrogen

37. Combustion Combustion of hydrocarbons ALWAYS produces CO2 and H2O C x H y + O 2 CO 2 + H 2 O

38. Ex problem show combustion of propane (C 3 H 8 ) gas show combustion of propane (C 3 H 8 ) gas C3H8C3H8 O2O2 CO 2 H2OH2O++1534