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Unit #12 Chemical Reactions

Unit #12 Chemical Reactions. Part 2 Predicting Products. Review. A chemical reaction is the rearrangement of atoms to form new substance(s). Reactant(s) appear on the left, and product(s) appear on the right. reactants product

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Unit #12 Chemical Reactions

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  1. Unit #12Chemical Reactions Part 2 Predicting Products

  2. Review • Achemicalreaction is the rearrangement of atoms to form new substance(s). Reactant(s) appear on the left, and product(s) appear on the right. reactants product • Example: 2 H2 + O2 2 H2O • When we look at any chemical reaction, in order for it to be accurate, it must show that the law of conservation of mass is obeyed.

  3. Law of Conservation of Mass • mass is neither created nor destroyed in a chemical reaction • total mass stays the same • atoms can only rearrange • So, we need to make sure that there are the same number of each type of atom on each side of the chemical equation. • To do this, we add coefficients in front of the compounds until these atoms are “balanced.”

  4. Refresh your memory by balancing these equations: __MgCl2 +__NaOH  __Mg(OH)2 +__NaCl __Fe2(SO4)3 +__KOH  __K2SO4 +__Fe(OH)3 2 2 6 3 2

  5. Synthesis Reaction A reaction in which two or more elements form a compound. 2 H2 + O2 → 2 H2O 3 Mg + N2→ Mg3N2

  6. Synthesis • 2 or more elements/compounds combine to form 1 product. • Only one product! • Analogy: Mixing 2 or more ingredients together to get 1 cake. . A + B  AB

  7. Synthesis Example: 2 Mg + O2 2 MgO Must crisscross to get new compound! Al(s)+ Cl2(g)  AlCl3(s) 2 3 2

  8. Practice Problems: • Na + F2 • B + N2  +1 -1 Na + F2 Na F BALANCE Na + F2 NaF 2 2

  9. Practice Problems: • Na + F2 • B + N2  +3 -3 B + N2 B N BALANCE B + N2 BN 2 2

  10. Decomposition Reaction A reaction in which a compound is broken down into two or more elements. 2 H2O → 2 H2 + O2 2HgO → 2 Hg + O2

  11. Decomposition • 1 compound is broken down into 2 or more simpler elements/compounds. • only one reactant • Analogy: A couple breaks up. Or a body decompses. AB  A + B

  12. Decomposition • Example Diatomic KBr  2 2 K + Br2

  13. Practice Problems: • Na2O  • CF4 Any Diatomic atoms? Na2O  Na O + 2 BALANCE Na2O  Na + O2 2 4

  14. Single Replacement Reaction A reaction in which one element reacts with one compound to form another element and another compound. 2 KCl + F2→ 2 KF + Cl2 Mg + 2 HCl → H2 + MgCl2

  15. Single Replacement • one element replaces another in a compound • metal replaces metal (+) • nonmetal replaces nonmetal (-) A + BC  B + AC

  16. Products: Metal replacement: 2 Na + CuCl2 2 NaCl + Cu Halogen replacement: F2 + 2 KCl  2 KF + Cl2 • free element must be more active(check activity series) Fe(s)+ CuSO4(aq)  Cu(s)+ FeSO4(aq) Br2(l)+ NaCl(aq)  N.R.

  17. Activity Series Activity Series

  18. Practice • Can Al replace Li? ____ • Can Cu replace Au? ____ • Can Br replace I? ____ • Can Cl replace F? ____ NO Yes YES NO

  19. Practice Problems: • H2 + PbCl2 • Cl2 + KBr  • Zn + CuS  +1 +2 -1 H2 + PbCl2 No rxn

  20. Practice Problems: • H2 + PbCl2 • Cl2 + KBr  • Zn + CuS  Any Diatomic atoms? +1 -1 -1 +1 -1 K Cl + Br Cl2 + KBr  2 BALANCE Cl2 + KBr  KCl + Br2 2 2

  21. Practice Problems: • H2 + PbCl2 • Cl2 + KBr  • Zn + CuS  Any Diatomic atoms? -2 +2 +2 +2 -2 Zn S + Cu Zn + CuS  BALANCE Zn + CuS  ZnS + Cu

  22. Double Replacement Reaction A reaction in which the metals present in two compounds change places to form two new compounds. Pb(NO3)2 + K2CrO4 PbCrO4+ 2 KNO3 NaCl + AgNO3 AgCl + NaNO3

  23. Double Replacement • Ions from 2 ionic compounds switch places. --put the inside ions together and the outside ions together • --positive ion always goes first in the compound! • Analogy: 2 couples are dancing, and they switch partners AB + CD  AD + CB

  24. Double Replacement Example: FeCl2 + Na2CO32 NaCl + FeCO3 Pb(NO3)2(aq)+ KI(aq)  PbI2(s)+ KNO3(aq)

  25. Practice #1 • Na2CO3 + Ca(NO3)2  • Na2CO3 + Ca(NO3)2  • Na2CO3 + Ca(NO3)2  NaNO3 +CaCO3 +2 -1 -2 +1 NaNO3 CaCO3 + 2 BALANCE

  26. Practice #2 • K3PO4 + MgCl2 • K3PO4 + MgCl2 • K3PO4 + MgCl2 KCl + Mg3(PO4)2 +1 -3 +2 -1 + KCl Mg3(PO4)2 2 3 6 BALANCE

  27. Combustion • When a carbon compound reacts with oxygen to make carbon dioxide and water. • Hint: • It will always have O2 on reactant side • It will always have CO2 and H2O on product side • Example: CH4 + O2→ CO2 + H2O

  28. Combustion • Also known as burning; always follows the same form: • The compound always burns in oxygen gas and always releases carbon dioxide and water. • During incomplete combustion (a limited amt. of O2), carbon monoxide (CO) is also produced. C & H (& sometimes O) + O2CO2 + H2O CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)

  29. Example: • 2 C3H6 + 9 O2 6 CO2 + 6 H2O *always balance in order: C, H, O • Practice Problems: CH4 + O2 C6H14 + O2 BALANCE CO2 + H2O 2 2 CO2 + H2O 2 19 12 14

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