MIssing: Blog for March 06, 2007

Sorry it took so long!
But you know what they say, "It's better late than never."

So, just a recap on March 06, 2007:

The "Oxidation-Reduction Compare and Contrast Frame" sheet and the "Redox Reactions" sheet were corrected and handed back.

Here are the corrections:
"Oxidation-Reduction Compare and Contrast Frame"
Oxidation
Historical Definition:
Any reaction that involved a reactant combining with oxygen was an oxidation reaction.
Example:
Burning substances - oxygen present.
Rusting / Corrosion - oxygen reacts with metal.

Present Definition:
A process by which a substance had given up their electrons.
Example:
Al(s) --------> Al³⁺_(aq) + 3e^-

Mnemonic Device:
O - Oxidation
I - Is
L - Losing
or
L - Losing
E - Electrons
O - Oxidation

When Balancing a Redox Reaction:
One substance is oxidized and it is also the reducing agent.
Its oxidation number increases.

Reduction
Historical Definition:
When oxygen is removed by a compound to produce a metal.
Example:
2Fe₂O₃(s) + 3C(s) ------> 4Fe(s) + 3CO₂(g)

Present Definition:
A process in which a substance gains electrons.
Example:
Al³⁺(aq)+ 3e^--------> Al(s)

Mnemonic Device:
R - Reduction
I - Is
G - Gaining
or
G - Gaining
E - Electrons
R - Reduction

When Balancing a Redox Reaction:
One substance is reducedand it is also the oxidizing agent.
It's oxidation number decreases.

"Redox Reactions"
1. Redox reactions are characterized by: d. transfer of electrons.
2. If a calcium atom loses two electron, it becomes: c. oxidized.
3. In a redox reaction, an oxidizing agent is: d. reduced.
4. An oxidation reaction occurs: a. at the same time a reduction reaction occurs.
5. Consider the equation Ca(s) + O₂(g) ------> 2CaO(s). In this reaction, calcium is oxidized because it: c. loses electrons.
6. The number of electron lost by an element when it forms ions is the element's: b. oxidation number.
7. A loss of electrons is: a. oxidation.
8. Redox reactions can involve: d. ions, molecules, or uncharged atoms.

9. - 15. Redox Reactions

Equation:
#16
Oxidized: Cd
Reduced: Ni²⁺
OA: NiO₂
RA: Cd

#17
Oxidized: Fe
Reduced: Cu
OA: SO4
RA: Fe

#18
Oxidized: Sb
Reduced: I
OA: I2
RA: Sb

#19
Oxidized: S
Reduced: O
OA: O2
RA: Cu2S

#20
Oxidized: Pb
Reduced: Pb⁺⁴
OA: PbO₂
RA: Pb

#21
Oxidized: N^-3
Reduced: N⁺⁵
OA: NH4NO3
RA: NH₄NO₃

#22
Oxidized: C
Reduced: Fe
OA: Fe₂O₃
RA: CO

FINALLY!

Ms. Kozoriz had written down steps on "Balancing Redox"

1. Assign oxidation numbers to each element.
2. Identify and write oxidation half reaction and reduction half reaction.
3. Balance in terms of electron numbers and atoms.
4. Add H2O and H to balance acidic reaction.
5. Do a change check for both half reactions.
6. Multiply through so electron number is the same in the reduction and oxidation half reaction.
7. Add both half reactions cancelling electrons and any other substances.
8. Do a final change check!

* Sorry again it took so long but we all know brilliance takes time =P.

By: Jennie