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 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.

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.”

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

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

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

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

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

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

Decomposition Example Diatomic KBr  2 2 K + Br2

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

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

Fe(s)+ CuSO4(aq)  Cu(s)+ FeSO4(aq) Br2(l)+ NaCl(aq)  N.R. 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.

Metals Nonmetals lithium fluorine potassium chlorine calcium bromine Activity Series Activity Series Metals Nonmetals lithium fluorine potassium chlorine calcium bromine sodium iodine magnesium oxygen aluminum nitrogen zinc chromium iron nickel tin lead hydrogen* copper mercury silver platinum gold

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

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

Any Diatomic atoms? K Cl Br Cl2 + KBr  BALANCE Cl2 + KBr  KCl + Br2 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

Any Diatomic atoms? Zn S Cu Zn + CuS  BALANCE Zn + CuS  ZnS + Cu 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

AB + CD  AD + CB 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

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

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

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

CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) 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)

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