1. Chemical Reactions
Chapter 10

2. For Science Fair Judges
Revised instructions!
Submit a list of projects that you judged with the associated grade-levels. A brief description of your impression of the projects would be helpful. (Be in SUB Ballroom by 5:00 PM for dinner and instructions.)
If you are not a judge, you may attend the Science Expo and write a detailed summary of at least two projects.
Either is extra-credit points or a lab make-up.

3. Types of Chemical Reactions
Oxidation-Reduction (Redox)
Combination
Decomposition
Replacement
Ion Exchange

4. Oxidation-Reduction Reactions
(electron transfer reactions)
Oxidation – an atom loses electrons
Reduction – an atom gains electrons
2 Mg (s) + O2 (g) MgO (s)
O2 is the oxidizing agent (takes electrons and
is reduced)
Mg is the reducing agent (supplies electrons and
is oxidized)
Mg2+O2-

5. Fig. 10.9 Example of an oxidizing agent (“chlorine”)
Others:
1) Bleach
2) Hydrogen
peroxide
3) Oxygen
4) Ultraviolet
light

6. Types of Chemical Reactions
Oxidation-Reduction (Redox)
Combination
Decomposition
Replacement
Ion Exchange

7. Fig. 10.10 Iron combines with oxygen to form rust (iron oxide)
4 Fe (s) + 3 O2 (g) Fe2O3 (s)

8. Hydrogen combines with oxygen to form water (dihydrogen monoxide)
                

9. Types of Chemical Reactions
Oxidation-Reduction (Redox)
Combination
Decomposition
Replacement
Ion Exchange

10. Fig. 10.11 Decomposition of Mercury Oxide
heat
2 HgO (s) → 2 Hg (l) + O2 (g)

11. Decomposition of Hydrogen Peroxide
2 H2O2 (l) → 2 H2O (l) + O2 (g)
(Demo)

12. Types of Chemical Reactions
Oxidation-Reduction (Redox)
Combination
Decomposition
Replacement
Ion Exchange

13. Fig. 10. 13 Replacement reaction between aluminum
Fig Replacement reaction between aluminum metal and the blue copper chloride solution
2 Al (s) 3 CuCl2 (aq) → 2 AlCl3 (aq) Cu (s) Cu Al
AlCl3
CuCl2

14. Replacement reactions take place when a more active metal gives up electrons to a less active metal.
How do we know if a replacement reaction will take place or not occur?
Refer to the activity series
Fig 10.12, p 264

15. Fig. 10.12 The activity series for common metals
2 Na + 2H2O NaOH + H2 ↑
(Demo)
Zn + 2HCl ZnCl2 + H2 ↑
(Demo)

16. Types of Chemical Reactions
Oxidation-Reduction (Redox)
Combination
Decomposition
Replacement
Ion Exchange

17. 2 KI + Pb(NO3)2 → PbI2 ↓ + 2 KNO3
Pg 253
PbI2

18. Ion Exchange Reaction – ions of one compound
react with ions of another compound to form:
(1) a solid (precipitate) or
FeCl NaOH → Fe(OH) NaCl
(2) a gas or (3) water
CaCO3 + 2 HCl → CaCl2 + CO2 ↑ + H2O
CaCO

19. Atomic mass is the mass of an atom in atomic mass units (u)
Micro World
atoms & molecules
Macro World
grams
Atomic mass is the mass of an atom in atomic mass units (u)
By definition:
1 atom 12C “weighs” 12 u
On this scale
1H = u
16O = u

20. Average atomic mass of lithium:
Natural lithium is:
7.42% 6Li (6.015 u)
92.58% 7Li (7.016 u)
Average atomic mass of lithium:
(7.42 · 6.015) + (92.58 · 7.016)
100
= u

21. Average atomic mass (6.941)

22. Dozen = 12 Pair = 2 mole - the amount of a substance that
contains as many particles as there
are atoms in exactly grams of 12C
1 mol = NA = x 1023
Avogadro’s number (NA)

23. Molar mass - the mass of 1 mole of in grams marbles atoms
eggs
shoes
Molar mass - the mass of 1 mole of in grams
marbles
atoms
1 mole 12C atoms = x 1023 atoms = g
1 12C atom = u
1 mole 12C atoms = g 12C
1 mole lithium atoms = g of Li
For any element
atomic mass (u) = molar mass (grams)

24. One Mole of: S C Hg Cu Fe

25. molecular mass (u) = molar mass (grams)
Molecular mass (or molecular weight) - the sum of
the atomic masses (in u) in a molecule.
SO2 1S
32.07 u 2O
+ 2 x u
SO2
64.07 u
For any molecule
molecular mass (u) = molar mass (grams)
1 molecule SO2 = u
1 mole SO2 = g SO2