1. Classification of Chemical Reactions
Physical Science
Sleevi

2. Chemical Reactions The process of chemical change
Substances are transformed to different substances
Indicators:
formation of precipitate
unexpected color change
evolution of gas
release or absorption of energy

3. Chemical Reaction
A + B  C + D

4. The Language of Reactions
Reactant
starting material of a chemical reaction
appears to the left of the reaction arrow
Product
substance formed in chemical reaction
appears to the right of the reaction arrow
Reaction Conditions
solvent, energy applied, catalysts, etc.

5. 2Na (s) + 2H2O (l)  H2 (g) + 2NaOH (aq)
Chemical Equations
2Na (s) + 2H2O (l)  H2 (g) + 2NaOH (aq)
s = solid
l = liquid
g = gas
aq = aqueous solution

6. Specific Temperature = 50oC
Reactions Conditions
Heat = Δ
Electricity = e-
Light = hv or γ
Catalyst = Pt
Specific Temperature = 50oC

7. CaCO3 (s)  CO2 (g) + CaO (s)
Chemical Reaction
Calcium carbonate is heated strongly and carbon dioxide gas is driven off, leaving a residue of calcium oxide.
CaCO3 (s)  CO2 (g) + CaO (s)

8. Descriptions of Chemical Reactions
Identify reactants by language such as:
is heated strongly
decomposes
is combined with
when added to
reacts with
neutralizes
x is converted to…

9. Descriptions of Chemical Reactions
Identify products by language such as:
is formed
produced
precipitates
is given off
is evolved
leaving a residue of
is converted to y

10. Writing Chemical Equations from Descriptions of Reactions
Identify reactants and products
Write correct chemical formulas
Identify and document states of each substance
Record reaction conditions (if given) above/below reaction arrow

11. Elements as Diatomic Molecules
Seven elements occur as diatomic molecules
hydrogen H2
nitrogen N2
oxygen O2
fluorine F2
chlorine
Cl2
bromine
Br2
iodine I2

12. Examples
Bubbling chlorine gas through a solution of potassium iodide gives elemental iodine and a solution of potassium chloride.
Solid silver oxide can be heated to give silver and oxygen gas.

13. Driving Forces for Chemical Reactions
Formation of a solid
Formation of water
Formation of a gas
Transfer of electrons
(Reactions are spontaneous if the products are favored)

14. Types of Chemical Reactions
Decomposition
Combination
Single Replacement
Double Replacement
Complete Combustion of Hydrocarbons

15. Decomposition Reactions
Single substance broken down into two or more simpler substances
Reactant must be compound
Products can be elements or compounds
Require input of energy to occur (light, heat, electricity)
A  B + C

16. Decomposition Reactions
2H2O  2H2 + O2
2H2O2  2H2O + O2
K2CO3  K2O + CO2
2KOH  K2O + H2O

17. Decomposition Reactions
Binary compound decomposes to elements
Metal carbonate decomposes to metal oxide and carbon dioxide
Base decomposes to metal oxide and water

18. Combination Reactions
Two or more substances form one product
Reactants can be elements or compounds
Product is always a compound
A + B  C

19. Combination Reactions
Na (s) + Cl2 (g)  NaCl (s)
SO3 (g) + H2O (l)  H2SO4 (aq)
K2O (s) + H2O (l)  KOH (aq)

20. Combination Reactions
Two elements combine to form a binary compound
metal + nonmetal  ionic compound
nonmetal + nonmetal  molecular compound
Nonmetal oxide + water  acid
Metal oxide + water  base

21. Single Replacement Reactions
Substitution reactions in which an element replaces the element in an ionic compound
metal replaces metal
halogen replaces halogen
metal replaces hydrogen (in an acid)
Not all reactions occur
A + BX  AX + B

22. Single Replacement Reactions
Mg + ZnCl2  MgCl2 + Zn
Fe + CuSO4  FeSO4 + Cu
Na + H2O  NaOH + H2
F2 + KCl  KF + Cl2

23. Single Replacement Reactions
Activity Series provides reference for which single replacement reactions occur
Note:
All examples we will use are reactions that occur. You will not need to use the activity series to determine whether or not a reaction occurs

24. Double Replacement Reactions
Exchange of positive ions between two compounds
Usually occur between ionic compounds in aqueous solutions
When reaction occurs
a precipitate forms
water or other molecular compound is formed
evolution of a gas

25. Double Replacement Reactions
Na2S (aq) + Cd(NO3)2 (aq)  NaNO3 (aq) + CdS (s)
NaCN (aq) + H2SO4 (aq)  HCN (g) + Na2SO4 (aq)
AgNO3 (aq) + KCl (aq)  AgCl (s) + KNO3 (aq)
NaOH (aq) + H2SO4 (aq)  Na2SO4 (aq) + H2O (l)

26. Combustion Reactions Hydrocarbon burns in the presence of oxygen
For complete combustion the products are ALWAYS carbon dioxide and water

27. Combustion Reactions CH4 + O2  CO2 + H2O C6H12O6+ O2  CO2 + H2O