1. Chemical Reactions: evidence, writing them, balancing them Zumdahl Chapter 6 Notes Start Date: ______

2. Clues of Chemical Reactions
1.Color changes Ex: 2. Solid forms (precipitate) 3. Gas forms 4. Heat is produced or absorbed

3. Writing Chemical Equations
Chemicals present before reaction are called: reactants, and are shown on the left side of the equation
Chemicals present after the reaction are called: products, and are shown on the right side of the equation.
ID the reactants and products (by name) in the following equation:
CO2(g) + H2O(l)  H2CO3(aq)

4. Writing unbalanced chemical equations
Look for key words that indicate whether the chemicals are reactants or products
Reactant phrases
A + B “react”
A “decomposes” “to form”
A “will produce” Z “when combined with B”
Product phrases
...”to form Y and Z”
…”to produce Y and Z”
…”will result in formation of Z”

5. Try these out! Write the unbalanced chemical equation for each of the following reactions
When barium peroxide is added to water, hydrogen peroxide and a precipitate of barium oxide forms. BaO2(aq) + H2O(l)  BaOH(s) If aqueous solutions of potassium chromate and barium chloride are mixed, a bright yellow solid (barium chromate) forms and settles out of the mixture, leaving potassium chloride in solution. K2CrO4(aq) + BaCl2(aq)  BaCrO4(s) + KCl(aq)

6. Balancing Chemical Equations
The process of adding numerical coefficients in front of compounds in chemical equations to ensure that law of conservation of matter is satisfied. NEVER touch the numerical subscripts!
Write the unbalanced form of the chemical reaction, including all states of matter subscripts
Balance the rxn by putting in numerical coefficients as necessary

7. How to Balance Chem. Eq’ns
Write the unbalanced equation w/subscripts
Make a 2 x 2 T-table underneath the unbalanced equation
In the first cell on left, write initial counts of reactants and circle to indicate compounds. Do the same with products
4. In the cells underneath initial counts, write overall counts, making symbols line up from reactants to products
5. Multiply by coefficients at the initial count bubbles level, and update final counts. Adjust as needed, and then record final coefficients.
CH4(g) + O2(g)  CO2(g) + H2O(g)
C: 1 O: 2 C: 1 H: 2
H: 4 O: 2 O: 1
C: 1 C: 1
H: 4 H: 2
O: 2 O: 3

8. Driving forces for chemical reactions
Formation of a solid
Formation of a gas
Formation of water
Transfer of electrons

9. Chemical Reactions Oxidation-Reduction (redox) synthesis
combustion
synthesis
R: CxHxOx + O2(g)
P: CO2(g) + H2O(g)
Met. + nmet. in el. form
Nmet. + O2(g) in el. form

10. Chemical Reactions: Combustion
In the flaming dollar bill combustion, ethanol (C2H6O) and oxygen gas combine to form carbon dioxide gas and water vapor. Write the full balanced equation for this reaction

11. Chemical Reactions: Combustion
In the methane bubbles demonstration, we reacted methane gas (CH4) with oxygen gas to produce carbon dioxide gas and water vapor.

12. Chemical Reactions: Single Displacement and Synthesis
In the “Filling and Popping a Balloon” reaction, zinc metal reacts with hydrochloric acid to form hydrogen gas and aqueous zinc (II) chloride. Write the full balanced equation.
We then react the hydrogen gas with the oxygen gas to produce water vapor. Write the full balanced equation.

13. Gummy Bear Demise!
In the gummy bear demise, we heated up the solid potassium chlorate to decompose the potassium chlorate into solid potassium chloride and oxygen gas. The oxygen gas then reacts with the sucrose in the gummy bear in a combustion reaction. Write the complete balanced equation for the potassium chlorate decomposition only.

14. Lights out.
The conductivity apparatus is put into aqueous sulfuric acid light bulb lights
A barium hydroxide solution is added drop by drop to the sulfuric acid solution to form water and a precipitate of barium sulfate  light bulb goes out
Write the complete balanced equation for the reaction of aqueous barium hydroxide and aqueous sulfuric acid.

15. Types of Redox Reactions
combustion – reaction between hydrocarbon (CxHxOx) and O2(g)  CO2(g) and H2O
Synthesis – rxn b/w a metal and nonmetal in their elemental forms  ionic cmpd, or a rxn b/w a nonmetal and oxygen, both in elemental forms
Decomposition – rxn where one cmpd breaks down into more than one simpler cmpd
Single Displacement-A free element (usu. metal) displaces another element (usu. metal) from a compound (usu. ionic compound) A + BC  AC + B

16. Chemical Reactions Oxidation-Reduction (redox) synthesis
combustion
synthesis
decomposition
single displacement
R: CxHxOx + O2(g)
P: CO2(g) + H2O(g)
Met. + nmet. in el. form
Nmet. + O2(g) in el. form
One R, more prod.
A + BC  AC + B

17. Chemical Reactions: Decomposition
In the “Elephant’s toothpaste” reaction, the decomposition of aqueous hydrogen peroxide is catalyzed by a solution of potassium iodide to create very hot water vapor and oxygen gas.

18. Redox Reactions- That’s where those ionic compounds come from!
Redox reactions- involve the transfer of electrons
1 example: when a metal (in elemental form) reacts with a nonmetal (in elemental form)
 Ionic compound
this is what type of reaction? (synthesis)
Transfer of e’s from the metal to the nonmetal.

19. Example Na(s) + Cl2(g)  2NaCl(s)
reactant charges charges in compound produced
Na 0 Na +1
Cl 0 Cl -1
1 electron(s) were transferred from Na to Cl
LEOGER (loss of electrons = oxidation, gain of electrons = reduction)

20. Single Displacement and the Activity Series
In order for A to displace B, A must be more reactive than B
A + BC  AC + B
Will this reaction occur? Predict the products:
Li(s) + NaCl(aq)  Na(s) +LiCl(aq)

21. Classify each type of reaction and balance
Cs(s) + Br2(l)  CsBr(s)
synthesis: Cs(s) + Br2(l)  2CsBr(s)
C2H2(g) + O2(g)  CO2(g) + H2O(l)
combustion: C2H2(g) + 3O2(g)  2CO2(g) + 2H2O(l)
PBr3(l)  P4(s) + Br2(l)
decomposition: 4PBr3(l)  P4(s) + 6Br2(l)

22. Classify each type of Redox Reaction, predict the products, and balance each
H2O2(l) 
decomposition: 2H2O2(l)  2H2O(g) + O2(g)
F2(g) + Ca(s) 
synthesis: F2(g) + Ca(s)  CaF2(s)
C2H4(g) + O2(g) 
combustion: C2H4(g) + 6O2(g)  2CO2(g) + 2H2O(g)

23. Classify each type of Redox Reaction, predict the products, and balance each
Fe(s) + CuSO4(aq) 
Single displacement: Fe(s) + CuSO4(aq)  Cu(s) + FeSO4(aq)
Cu(s) + FeSO4(aq) 
Cu(s) + FeSO4(aq)  NO RXN (copper is not more reactive than iron)

24. Chemical Reactions Double Displacement Oxidation-Reduction (redox)
precipitation
acid-base
P: one aq. Ionic cmpd, one solid ionic cmpd (precipitate)
R: two aq. ionic cmpds
combustion
synthesis
decomposition
single displacement
R: strong acid and strong base
P: water and ionic cmpd (aq. or solid)
R: CxHxOx + O2(g)
P: CO2(g) + H2O(g)
Met. + nmet. in el. form
Nmet. + O2(g) in el. form
One R, more prod.
A + BC  AC + B

25. Double Displacement (DD) Reactions: precipitation and acid-base
Because ionic compounds that dissolve in water separate into their cation and anion components (each surrounded by water):
AB(aq) + CD(aq)  AD + CB
the products can be:
both aq. (no reaction)
one aq. and one ppt. (precipitation)
one aq. and one water (acid-base)
one ppt. and one water. (acid-base)

26. Predicting the products of precipitation reactions
Switch the cations and anions to predict products (make sure you consider charges and write cation first in each new formula)
Predict the states of matter subscripts of products using solubility table (provided), if both aq. products, no reaction
Soluble
Insoluble
Most NO3- Salts
Most salts of Na+, K+, and NH4+
Most chloride salts (Cl-) and iodide and bromide salts
AgCl, PbCl2, Hg2Cl2,Those containing Ag, Hg, Pb
Most sulfate (SO42-) salts
BaSO4, PbSO4, CaSO4
NaOH and KOH
Most hydroxide () compounds. Ba(OH)2 and Ca(OH)2 only moderately soluble
Most sulfide (S2-) carbonate (CO32-) and phosphate (PO43-) salts

27. Let’s try some!!
Predict the products of the following reactions, and then balance the equations (if a reaction occurs) FeSO4(aq) + KCl(aq)  FeSO4(aq) + KCl(aq)  NO REACTION (both aqueous prod.) FeCl3(aq) + H3PO4(aq)  FeCl3(aq) + H3PO4(aq)  3HCl(aq) + FePO4(s) (NH4)2S(aq) + CuCl2(aq)  (NH4)2S(aq) + CuCl2(aq)  2NH4Cl(aq) + CuS(s)

28. The complete ionic equation
A complete ionic equation shows
all aqueous ionic compounds separated into their ions
Molec. eq’n: Pb(NO3)2(aq) + 2KI(aq)  PbI2(s) + 2KNO3(aq)
Comp. ionic eq’n:
Pb2+(aq) + 2NO3-(aq) + 2K+(aq) + 2I-(aq)  PbI2(s) + 2K+(aq) + 2NO3-(aq)
Net ionic eq’n: Pb2+(aq) + 2I-(aq)  PbI2(s)

29. The net ionic equation A net ionic equations shows only
the compounds directly participating in the reaction
Comp. ionic:
Pb2+(aq) + 2NO3-(aq) + 2K+(aq) + 2I-(aq)  PbI2(s) + 2K+(aq) + 2NO3-(aq)
Net ionic eq’n: Pb2+(aq) + 2I-(aq)  PbI2(s)

30. Try these on your own
Write the net ionic equation for the following reaction:
BaCl2(aq) + Na2SO4(aq)  BaSO4(s) + 2NaCl(aq)
Ba2+(aq) + SO42-(aq) BaSO4(s)

31. Keep going! What is the net ionic equation for the following reaction?
(NH4)2SO4(aq) + CaCl2(aq)  2NH4Cl(aq) + CaSO4(s)
Ca2+(aq) + SO42-(aq) +  CaSO4(s)

32. Acids and bases
Acids produce H+ ions when dissolved in water (strong acids will donate all protons)
Bases produce OH- ions when dissolved in water (strong bases will accept a proton for every OH-) H+
Cl- H+ Cl-
H Cl-
Na+
Na+ OH- Na+
OH- OH-

33. Reactions of Strong Acids and Strong Bases
water is created when a strong acid reacts with a strong base
Increasing Strength as go towards top
Strong Acids
Strong Bases
HClO4
KOH HI
Ba(OH)2
HBr
CsOH
HCl
NaOH
H2SO4
Sr(OH)2
HNO3
Ca(OH)2
LiOH
RbOH

34. Determine the balanced molecular equation, the complete ionic equation, and the net ionic equation
HNO3(aq) + KOH(aq) 
b. mole. equation: HNO3(aq) + KOH(aq)  H2O(l) + KNO3(aq)
com. ionic eq’n: H+(aq) + NO3-(aq) + K+(aq) + OH-(aq)  H2O(l) + K+(aq) + NO3-(aq)
net. Ionic eq’n: H+(aq) + OH-(aq)  H2O(l)

35. hydrochloric acid plus sodium hydroxide 
Determine the balanced molecular equation, the complete ionic equation, and the net ionic equation
hydrochloric acid plus sodium hydroxide 
HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)
Complete ionic equation:
H+ (aq) + Cl-(aq) + Na + (aq) + OH-(aq)  Na + (aq) + Cl-(aq) + H2O(l)
Net ionic equation:
H+ (aq) + OH-(aq)  H2O(l)

36. Try some on your own!
Solid barium peroxide is added to water to form aqueous hydrogen peroxide and a precipitate of barium oxide. Write then balance.
BaO2(s) + H2O(l)  H2O2(aq) + BaO(s)
Fe3O4(s) + CO(g)  Fe(s) + CO2(g)
(disregard this one– it’s incorrect as written)