Good Morning Ladies!
1. Questions before the test?
2. TEST
In both fission and fusion reactions, energy is…
RELEASED
because…
E = mc2
Energy = mass x speed of light squared
Mass is converted to energy
100 g samples of both radium-226 and radon-222
were left in a chemical laboratory in 1950. Which
sample poses the least risk today?
Half-life of radium-226 is 1600y
Half-life of radon-222 is 3.82d
• radon-222 because it has a shorter half-life
• radon-222 because it decays faster
Good Afternoon Ladies!
1. Questions before the test?
2. TEST
…………….
3. Begin Oxidation-Reduction Reactions Unit
In both fission and fusion reactions, energy is…
RELEASED
because…
E = mc2
Energy = mass x speed of light squared
Mass is converted to energy
100 g samples of both radium-226 and radon-222
were left in a chemical laboratory in 1950. Which
sample poses the least risk today?
Half-life of radium-226 is 1600y
Half-life of radon-222 is 3.82d
• radon-222 because it has a shorter half-life
• radon-222 because it decays faster
Good Morning Ladies!
• Prayer
• Regents Review Resources
• Begin Oxidation-Reduction Reactions Unit
– What are oxidation-reduction reactions?
– Assigning oxidation numbers
HW: Redox 1 DUE MONDAY
Also: Simulating Half-Life Lab DUE next Friday
Oxidation-Reduction Reactions
*What kind of chemical reaction is responsible for
burning, rusting, bleaching clothes, powering your
cell phone as well as your body, and giving fireflies
their glow?
• Oxidation-Reduction Reactions, also called
REDOX reactions
I. What are Redox Reactions?
• Redox reactions involve the transfer of
ELECTRONS (e–) between different atoms
Na + Cl → Na
+ Cl
Oxidation
Reduction
* CONSERVATION OF CHARGE: oxidation and
reduction happen simultaneously (at the
same time) – you can’t have one without the
other
Remember:
LEO the lion says GER
(or LEO the liger says GER)
• LOSING ELECTRONS is OXIDATION
• GAINING ELECTRONS is REDUCTION
Good Afternoon Ladies!
• Determining if a reaction is redox
• Assigning oxidation numbers
HW: Redox 1 DUE MONDAY
Also: Simulating Half-Life Lab DUE next Friday
II. Determining if a reaction is a redox reaction
• If the oxidation number/state of an atom
changes from reactant to product, a redox
reaction has occurred
*Note: Double replacement reactions are NOT
redox reactions
A. Assigning Oxidation Numbers
(listed on the Periodic Table)
1. If a species is all by itself (not combined with
a different element), its oxidation number is
ZERO
Ex:
Mg
O2
S2
Cu
H2
A. Assigning Oxidation Numbers
(listed on the Periodic Table)
2. In a polyatomic ion, the elements’ oxidation
numbers add up to equal the CHARGE on the ion
* SOS: you must multiply the Subscript by the
Oxidation number to get the Sum
NH4
+
–
ClO
A. Assigning Oxidation Numbers
(listed on the Periodic Table)
2. In a polyatomic ion, the elements’ oxidation
numbers add up to equal the CHARGE on the ion
* SOS: you must multiply the Subscript by the
Oxidation number to get the Sum
SO3
2–
SO4
2–
A. Assigning Oxidation Numbers
(listed on the Periodic Table)
3. In a compound, the oxidation numbers of the
elements add up to ZERO (compounds are
neutral)
* SOS: you must multiply the Subscript by the
Oxidation number to get the Sum
NaCl
A. Assigning Oxidation Numbers
(listed on the Periodic Table)
3. In a compound, the oxidation numbers of the
elements add up to ZERO (compounds are
neutral)
• SOS: you must multiply the Subscript by the
Oxidation number to get the Sum
NH4Cl
A. Assigning Oxidation Numbers
(listed on the Periodic Table)
3. In a compound, the oxidation numbers of the
elements add up to ZERO (compounds are
neutral)
• SOS: you must multiply the Subscript by the
Oxidation number to get the Sum
H2SO3
More Examples
a.) What is the oxidation number of chlorine in
iron (III) chloride?
More Examples
b.) What is the oxidation state of chromium in
potassium chromate?
B. Checking for Changes in Oxidation Numbers
2 Na (s) + Cl2 (g) → 2NaCl (s)
•
•
•
•
The oxidation # on Cl
Nachanges
changesfrom
from00to
to–1
+1
Nagains
loseselectrons
electrons
Cl
Na
oxidized
Cl isisreduced
Naisisthe
theoxidizing
reducingagent
agent
Cl
B. Checking for Changes in Oxidation Numbers
2Mg (s)
•
•
•
•
+
O2 (g)
→
2MgO (s)
Mgchanges
changesfrom
from0 0toto–2+2
The oxidation # on O
Mggains
loseselectrons
electrons
O
Mgisisreduced
oxidized
O
Mgisisthe
theoxidizing
reducingagent
agent
O
Orange Packet
• #s 1, 21, 23, 25
Good Morning Ladies!
•
•
•
•
Prayer
Review Videos on Wikispace!
Trade & Grade Redox 1 (collect)
Writing Oxidation & Reduction Half-Reactions
HW: Redox 2 DUE WEDNESDAY
Reminder: Simulating Half-Life Lab DUE FRIDAY
Good Afternoon Ladies!
• Review Videos on Wikispace!
• Trade & Grade Redox 1 (collect)
• Writing Oxidation & Reduction Half-Reactions
HW: Redox 2 DUE WEDNESDAY
Reminder: Simulating Half-Life Lab DUE FRIDAY
a.) Zn + 2HCl → ZnCl2 + H2
b.)
4Al + 3O2 → 2Al2O3
c. For soldiers on the front lines or on special remote missions, a hot meal can make
a big difference. Instead of building a fire or carrying a stove with them, soldiers
simply break open a bag and mix some magnesium metal with water to heat
their food. This reaction is an example of a redox reaction, producing
magnesium hydroxide, hydrogen gas, and heat as products. In the space below,
write the oxidation and reduction half-reactions.
Whiteboard Practice
Write the oxidation and reduction half-reactions
for the following redox reactions
Zn + HNO3  Zn(NO3)2 + NO2 + H2O
Sn + HNO3 + H2O  H2SnO3 + NO
NaClO + H2S  NaCl + H2SO4
Orange Packet
#s 2, 3, 19, 20, 22, 24, 26-30, 32-35
Good Morning Ladies! (TUES)
•
•
•
•
•
Prayer
Gummy Bear Sacrifice
Breathalyzer Demo
Balancing Redox Reactions
Pass back Nuclear Chemistry Test
HW: Redox 2 DUE TOMORROW
Reminder: Simulating Half-Life Lab DUE FRIDAY
In the presence of oxygen, iron forms iron (III) oxide, more
commonly known as rust. In the space below, write the
balanced equation for the chemical process of the corrosion of
iron using the oxidation and reduction half-reaction method.
What causes fruit to turn brown?
• Oxidation of compounds in fruit after
exposure to oxygen in the air causes a change
of color (browning) of fruit
Oxidation (losing electrons) is a process that can
be very damaging to living things.
• results in the creation of free radicals, which
are chemical species that have unpaired
electrons (they are unhappy – they don’t have
a completed valence shell)
• free radicals will rip electrons away from other
compounds in living things, such as proteins
or molecules of DNA, causing damage which
can lead to cancer
• Antioxidants get rid of free radicals
– Vitamins A, C, and E are antioxidants
Good Morning Ladies! (WED)
Please place your Redox 2 HW in the bin
• Prayer
• Two Types of Electrochemical Cells
– Voltaic cells
– Electrolytic cells
Reminder: Simulating Half-Life Lab DUE FRIDAY
Heads up HW: Redox 3 DUE TUESDAY
*Redox Unit TEST next WEDNESDAY
Good Afternoon Ladies! (WED)
Please place your Redox 2 HW in the bin
• Two Types of Electrochemical Cells
– Voltaic cells
– Electrolytic cells
Reminder: Simulating Half-Life Lab DUE FRIDAY
Heads up HW: Redox 3 DUE TUESDAY
*Redox Unit TEST next WEDNESDAY
V. Electrochemical Cells
A. Use REDOX reactions to convert chemical
energy into electrical energy OR convert
electrical energy into chemical energy
1. Voltaic (Galvanic) Cells = batteries
a.) SPONTANEOUS redox reactions – NO energy
put in (energy is released)
Use Table J to determine what is oxidized
and what is reduced
Higher on Table J is OXIDIZED
Lower on Table J is REDUCED
*Parts to Know*
Electrodes: the places where oxidation
or reduction happens
o Anode: the site of oxidation (An Ox)
o Cathode: the site of reduction (Red Cat)
Wire: electrons flow through the wire
from the anode (–) to the cathode (+)
Salt bridge: allows IONS to flow between
the electrodes to keep the charges
balanced
The electrodes must be separated in order to
produce an electric current (flow of electrons).
The energy present in the flowing electrons
(ELECTRICITY) is captured and used to power
other processes.
b.) Diagram of a voltaic cell using Zn and Zn(NO3)2
with Cu and Cu(NO3)2
c.) Voltaic cell problems:
1. Look on Table J and find which element is
higher – this element is OXIDIZED
(On Table J – electrons flow DOWNHILL,
spontaneously)
2. Under each beaker write “oxidation” or
“reduction”
3. Label the oxidation electrode ANODE (An Ox)
4. Label the reduction electrode CATHODE
(Red Cat)
5. Place a (–) charge on the anode
6. Place a (+) charge on the cathode
7. Draw in the direction of electron flow (from
ANODE (–) to CATHODE (+))
8. Write the half reactions under the correct
beakers
9. Be able to describe what is occurring at the
anode and cathode
10. The salt bridge allows for ions to flow
between the electrodes
Positive (+) ions flow toward the CATHODE
(to balance the negative electrons)
Negative (–) ions flow toward the ANODE
(to replace the electrons that are leaving)
How many of you have had cavities filled?
…if you do, you have the potential to make a
tiny battery IN YOUR MOUTH!
• Cavities are filled with a mixture of metals
including zinc (Zn), tin (Sn), copper (Cu), and
silver (Ag)
• If you bite down on a piece of aluminum foil,
the saliva in your mouth, the aluminum foil,
and the filling make a little voltaic cell that
produces a tiny current that travels through
your tooth to the nerve below the filling…it’s a
bit UNPLEASANT!
Voltaic cell animation
• http://www.blackgold.ab.ca/ICT/Division4/Sci
ence/Div.%204/Voltaic%20Cells/demo.htm
Orange Packet
#s 4-12, *16, 36, 37, 39
2. Electrolytic Cells
a.) NONSPONTANEOUS redox reactions – need
to put in energy
b.) The species more likely to lose electrons is
forced to gain electrons
(On Table J – electrons are moving UPHILL,
nonspontaneously)
2. Electrolytic Cells
c.) Electrons still flow from the anode to the
cathode, but now the signs are reversed
• The anode is (+) and the cathode is (–)
(electrons are being forced to travel to the
negative electrode)
2. Electrolytic Cells
d.) Used for
1. Electrolysis: using electricity to
break apart (lyse) compounds into their
elements
Ex: Obtaining active elements from compounds
2NaCl (l)
2. Electrolytic Cells
d.) Used for
1. Electrolysis: using electricity to
break apart (lyse) compounds into their
elements
Ex: Obtaining active elements from compounds
2H2O (l)
2. Electrolytic Cells
d.) Used for
2. Electrolytic cells can also be used for
electroplating – putting a metal coating on
something
Anode:
Cathode:
Comparing & Contrasting Voltaic and Electrolytic Cells
Voltaic Cells (Batteries)
• SPONTANEOUS
redox rxn
• energy is produced
(electricity)
• anode is (-)
• cathode is (+)
Electrolytic Cells)
• nonspontaneous
redox rxn
• energy is needed
(needs electricity)
• anode is (+)
• cathode is (-)
Comparing & Contrasting Voltaic and Electrolytic Cells
Voltaic Cells (Batteries)
Electrolytic Cells)
• redox reactions
• anode is where oxidation happens
(An Ox)
• anode loses mass
• cathode is where reduction happens
(Red Cat)
• cathode gains mass
• electrons flow through wire
from anode to cathode
Orange Packet
#s 13-15, *17, *18, 38, 40-61
Bioluminescence vs. Fluorescence
• Redox
reaction
produces
excited
electrons
• External
energy
source
excites
electrons
• Spectral
lines
• UV light
demos
• CuSO4 in Zn
• Hydrolysis of water