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Unit #8 Chemical Reactions

Unit #8 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 Example: 2 H 2 + O 2  2 H 2 O

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Unit #8 Chemical Reactions

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  1. Unit #8Chemical 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 • 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

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

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

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

  9. 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

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

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

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

  13. 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.

  14. Activity Series Activity Series

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

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

  17. 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

  18. 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

  19. 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

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

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

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

  23. 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)

  24. 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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