1. Pick up Homework sheet!

2. Chemical Reactions
Chapter 11

3. Today’s Objectives
Be able to indicate when a chemical change has occurred.
Understand the Law of Conservation of Mass

4. What is a chemical reaction?
A change in which one or more reactants change into one or more products
Characterized by the breaking of bonds in reactants and the formation of bonds in products
A change that produces matter with a different composition than the original matter
Taking one thing and making it something completely different!

5. Indicators of a Chemical Change
Change in color
Heat absorbed or released
Formation of a gas
Formation of a precipitate
Odor given off

6. Balancing Equations Chemical Equation:
an expression that represents a chemical reaction.
Law of Conservation of Mass: No atoms are created or destroyed in chemical reactions. Atoms are just rearranged.
Reactants  Products
#atoms of each element in the reactants = # atoms of each element in the products

7. Chemical Reactions

8. 4 Types of Chemical Reactions
Synthesis
Decomposition
Single Replacement
Double Replacement

9. Synthesis Two or more reactants combine to form a single product.
4Fe (s) + 3O2 (g)  2Fe2O3 (s)
A B  AB

10. Decomposition A single reactant forms two or more products.
NH4NO3 (s)  N2O (g) + 2H2O (g)
AB  A B

11. Single-Replacement (Single Displacement)
One element takes the place of another element in a compound. (“cutting in”)
Cationic:
Fe (s) + CuSO4 (aq)  FeSO4 (aq) + Cu (s)
A BC  AC B
Anionic:
Cl2 (g) + 2NaBr (aq)  2NaCl (aq) + Br2 (l)
A BC  BA C

12. Double-Replacement (Double Displacement)
The positive ions of two ionic compounds switch places. (“switching partners”)
At least one of the products is a precipitate, water, or a gas.
Pb(NO3)2 (aq) + 2 KI (aq)  PbI2 (s) + 2 KNO3 (aq)
AB CD  AD CB

13. Acid-Base (Double Replacement)
An acid and base react to form water and a salt.
HCl(aq) + NaOH(aq)  H2O(l) + NaCl (s)
AB CD  AD CB
acid base  water + salt

14. Combustion Reaction
2 C2H2 (g) + 5 O2 (g)  4 CO2 (g) + 2 H2O (g) + energy
What makes our engines run.
Any time you burn an organic substance, you are creating a combustion reaction.
Often a hydrocarbon fuel burning in oxygen to produce CO2 & H2O.

15. Predicting Products Use Reference Table to predict type of reaction.
Guidelines for Predicting the Products of Selected Types of Chemical Reaction
Key: M = Metal
NM = Nonmetal
Predicting Products

16. Practice Match each reaction to the best fitting reaction type.
1. ____ C3H8 + O2 -> H2O + CO2
2. ____ Mg + O2 -> MgO
3. ____ Ca + HCl -> CaCl2 + H2
4. ___ KClO3 -> KCl + O2
5. ___ HCl + NaOH -> NaCl + H2O
6. ___ NaNO3 + Ag -> AgNO3 + Na
7. ___ CH4 + O2 -> CO2 + H2O
Reactions
A. Synthesis
B. Decomposition
C. Combustion
D.Single Displacement
E. Double Displacement

17. Chemical Reactions
Chapter 11

18. Warm Up for Tuesday, October 28
Match each reaction to the best fitting reaction type.
1. ____ C3H8 + O2 -> H2O + CO2
2. ____ Mg + O2 -> MgO
3. ____ Ca + HCl -> CaCl2 + H2
4. ___ CH4 + O2 -> CO2 + H2O
5. ___ Na + O2 -> Na2O
6. ___ H2SO4 + MgO -> H2O + MgSO4
7.___ H2O2 -> H2O + O2
Reactions
A. Synthesis
B. Decomposition
C. Combustion
D.Single Displacement
E. Double Displacement

19. Writing Chemical Reactions
Chemical Equation:
an expression that represents a chemical reaction.
A balanced chemical equation tells:
What elements and/or compounds are involved
The relative amounts of each substance involved
Chemical equations MUST:
Include the correct formula for the species involved
Satisfy the Law of Conservation of atoms
Tell the relative number of moles (quantity) of each species

20. Symbols you might see: Physical States: (g) – gas (l) – liquid
(s) – solid or precipitate
(aq) – substances dissolved in water
 - reversible arrow
reaction can go forward or backwards
Δ – heat involved in the reaction
MnO2 – catalyst
Substance that speeds up the reaction but is not used up in the reaction

21. How to write a balanced chemical equation:
1. Decide which species are reactants & which are products
2. Write each species as a correct chemical formula.
3. Write the formulas for the reactants on the left side of the paper.
4. Place an arrow () after the reactants to indicate what is produced.
5. Write formulas for the products on the right side of the arrow.
6. Balance the chemical equation by adjusting the coefficients in front of the species to satisfy the Law of Conservation of Atoms.
Same number of atoms of each element on both sides of the arrow
Reactants
Products
Yields

22. Law of Conservation of Atoms
During any chemical reaction, the mass of the products is always equal to the mass of the reactants.
Matter cannot be created or destroyed.
In any chemical reaction, mass is conserved.
We use coefficients to balance chemical equations so that it obeys the
Law of Conservation of Atoms!

23. Rules for Balancing an Equation:
1. Write out the numbers of each element for each side.
2. Add coefficients to balance elements ONE AT A TIME.
Keep a running tally of the numbers of each element.
Check each number after each coefficient added.
Balance complicated compounds FIRST.
Balance elements that appear alone or as diatomic molecules LAST.
Save Oxygen & Hydrogen for LAST.
3. Reduce coefficients to simplest ratio, if necessary.

24. Example:
Ammonium chloride reacts with calcium hydroxide to produce calcium chloride, ammonia, and water. 2
NH4Cl +
Ca(OH)2
CaCl2 + 2
NH3 + 2
H2O
N :
H :
Cl :
Ca :
O : 1 2
N :
H :
Cl :
Ca :
O : 1 2 6 10 5 8 10 1 2 2 1 1 2 1 2

25. Practice:
Write the chemical equation & balance:
Sodium hydrogen carbonate decomposes into sodium carbonate, carbon dioxide, and water.
NaHCO3  Na2CO CO H2O 2
Na 1
H 1
C 1
O 3
---- 2
---- 6
Na 2
H 2
C 2
O 6

26. Practice 1) ____ NaCl + ____ F2  ____ NaF + ____ Cl2
2) ____ H2 + ____ O2  ____ H2O
3) ____ Pb(OH)2 + ____ HCl  ____ H2O + ____ PbCl2

27. Today’s Objective Predict Products for Reactions using Reference Table
Understand the rules governing Single-Replacement Reactions
Complete the Reactivity of Metals Lab

28. Predicting Products using Reference Table
If you are two different elements as reactants
SYNTHESIS
If you have only one reactant
DECOMPOSITION
If you have an element (exculding O2) & a compound
SINGLE-REPLACEMENT
If you have two aqueous compounds
DOUBLE-REPLACMENT
If you have a hydrocarbon & O2
COMBUSTION

29. Use Reference Table to Decide which rule to use!
Example: Mg + O2 -> Mg + N2 ->
Mg+ O2
Mg3N2
Practice Predicting Products:
Ca + Cl2 ->
ZnCl2 ->
Li2O ->
K + S ->

30. Single Replacement Reactions
Use Activity Series to Determine if a Reaction Will Occur.
A lone element will replace an element in a compound if it is MORE REACTIVE (higher on chart).
The element that is by itself MUST be higher on the chart than the one in the compound!

31. Decide if the reaction will occur:
Fe (s) + Pb(NO3)2 (aq) 
Ni (s) + MgCl2 (aq) 
Cl2 (aq) + NaI (aq) 
Ca (s) + CuBr2 (aq) 
K (s) + Al(NO3)3 (aq) 
I2 (s) + MnBr2 (aq) 
Mg (s) + AgNO3 (aq) 
Cl2 (s) + SrF2 (aq) 
YES NO

32. Predict the Products Ca (s) + CuBr2 (aq)  K (s) + Al(NO3)3 (aq) 
I2 (s) + MnBr2 (aq) 
Mg (s) + AgNO3 (aq) 
Cl2 (s) + SrF2 (aq) 

33. Double Replacement Reactions
Reminder:
At least one product is a precipitate, water, or a gas.
Use solubility rules to determine which product is the precipitate.
Precipitate = solid (insoluble)
Both reactants are AQUEOUS.
Only ONE product can be AQUEOUS.
The other must be SOLID, LIQUID, or GAS.

34. Solubility Rules
Must know the NAME of the compound before determining its solubility!

35. Predicting Products Single Replacement Double Replacement
Use ACTIVITY SERIES
The element that is by itself MUST be higher on the chart than the element in the compound for the reaction to occur
Metal replace Metals
Nonmetals replace Nonmetals
Double Replacement
Use SOLUBILITY RULES
One product MUST be INSOLUBLE
Do NOT check solubility of reactants!

36. PbNO3(aq) + AgI(s) RbI (aq) + AgNO3 (aq)  Na3PO4 (aq) + MnCl2 (aq) 
Li2CO3 (aq) + MoBr6 (aq) 
Ca(NO3)2 (aq) + Al(OH)3 (aq) 
CuCl2 (aq) + Na2CO3 (aq) 
BaCl2 (aq) + K2SO4 (aq) 
NaCl(aq) + Mn3(PO4)2(s)
LiBr(aq) + Mo(CO3)3(s)
Ca(OH)2(s) + Al(NO3)3(aq)
NaCl(aq) + CuCO3 (s)
KCl(aq) + BaSO4 (s)

37. Reactions in Aqueous Solution
Ionic compounds dissociate into ions in water!
Overall equation: AgNO3(aq) + NaCl(aq) AgCl(s)+ NaNO3(aq)
Ionic Equation: Ag+(aq) +NO3- (aq) +Na+ (aq) +Cl- (aq) AgCl (s) +Na+ (aq) +NO3 (aq)
Shows dissolved ionic compounds as dissociated free ions
Only separate AQUEOUS compounds into ions!

38. Ag+(aq) +NO3- (aq) +Na+ (aq) +Cl- (aq) AgCl (s) +Na+ (aq) +NO3 (aq)
Net Ionic Equations
Ag+(aq) +NO3- (aq) +Na+ (aq) +Cl- (aq) AgCl (s) +Na+ (aq) +NO3 (aq)
Spectator ions:
Ions that do not participate in the reaction: Na+, NO3-
Net ionic equation:
Shows only ions that are active in the reaction: Ag+ (aq) + Cl- (aq)  AgCl (s)
Balancing Net Ionic Equations: must be balanced with respect to both mass (atoms) and charge.

39. Practice: Write the balanced net ionic equation.
Pb (s) + AgNO3 (aq)  Ag (s) + Pb(NO3)2 (aq)
FeCl3 (aq) + KOH (aq)  Fe(OH)3 (s) + KCl (aq)