Practice Links: https://docs.google.com/viewer?a=v&pid=sites&srcid=ZGVmYXVsdGRvbWFpbnxwbHVjaGlub2NoZW18Z3g6NTU1NDk4NTRiNTM2ZTk1Mw
Oxidation-Reduction reactions involve a transfer of electrons from the substance oxidized to the substance reduced
***LEO the lion says GER: loss of electrons is oxidation; gain of electrons is reduction
a. Rules for oxidation states:
i. The oxidation state of an atom in an element is always 0
ii. Oxidation state of a monoatomic atom is its charge
iii. In compounds, fluorine is -1
iv. Oxidation is always -2, except when it is combined with fluorine or in a peroxide
v. The oxidation state of Hydrogen is +1
b. Electron shift method
i. Divides reaction into two half reactions. These reactions are balanced by using the oxidation number, since charge is conserved.
ii. Multiply if electrons gained and reduced are different
iii. Finally the two equations are added together
c. Ion electron method
Electro Chem:
ElectroChemistry much like its name implies is about electricity in chemistry, duh...
More specifically electrochemistry, at least what we are learning about deals with cells.
We’re not talking about the cells you find in the body. More like electric cells if you couldn’t figure it out by yourself.
Quoted from the orange book “ an electrochemical cell involves a chemical reaction and a flow of electrons.
There are two types of cells we want to talk about:
Voltaic
Electrolytic
Voltaic Cell:
This is a pretty cool cell, and it also explains how a normal battery works. When I was a child I thought that there was just a bunch of electricity in a battery, however, that seems to not be the case.
Since I don’t like paraphrasing here is another quote: “A voltaic cell is an electrochemical cell in which a spontaneous chemical reaction produces a flow of electrons.”
From this we know that we need a reaction that is spontaneous that can also involve the transfer of electrons. That means we have to use an ionic bond of some sort for the equation. In addition for this transfer of electrons to happen we need an oxidation/ reduction reaction to happen.
Since now we know a few parts that are involved in this cell, I am going to show a diagram.
The overall reaction for this cell is Zn + CuSO4 -> Cu + ZnSo4. The reason why Zn can do this is because it is much more active than Cu, therefore it can replace Cu in the equation
We can ignore the SO4 in this equation because that is a bystander particle, and no one likes those. So the equation becomes Zn+ Cu= Cu+Zn. Now this doesnt make much sense unless you put oxidation numbers on the elements. Now look: Zn(0) + Cu(2+) = Cu(0)+ Zn(2+). From this we can clearly see that Zn is being oxidized, while Cu is being reduced in this equation.
Now lets apply the diagram to this equation. We know that Zn is being oxidized so we can label it as the anode (where oxidation occurs). Also because we know Cu is being reduced we can label that side as the cathode (where reduction occurs).
Oxidation is happening in the anode so electrons are being lost and and transferred through the wire. If the circuit is closed (it isn't in the picture) then the electrons go through the load and get transferred to the cathode. Since electrons are being added to Cu t it is being reduced.
The anode is the negative side which gives away electrons, and the cathode is the positive side that gains electrons, much like the sides in a battery.
If you don’t understand what I am saying, don’t ask me for help, go read the orange book.
Electrolytic cell:
An electrolytic cell requires an electric current (a battery) to force a non- spontaneous reaction to occur. Previously we have seen Zinc oxidize and give electrons to Cu, however, can the opposite take place? WELL YES!!! You just need a power source because the reaction isn’t spontaneous.
Before I go on I am going to clarify a term:
electrolysis: the process of using electricity to force a chemical reaction.
One purpose of the electrolytic cell is to obtain active elements (ones that are hard to find in nature because they always bond) by the electrolysis of fused salts. So using a electrolytic cell I would be able to separate molten NaCl to obtain the two highly active elements in their pure forms.
Another purpose is to electroplate metals onto a surface. For example I could coat Zn with Copper if I really wanted to.
Ok let us look at a electroplating example:
Ignore the guy on the right.
Ok, from this diagram we can see an anode of Ag silver. The anode is oxidizing creating Ag+ ions while transmitting electrons to the positive side of the battery. The anode metal piece has a positive charge due to oxidation. The electrons that were intercepted by the battery now flow out the negative side of the battery and are forced into the cathode. The cathode now has more electrons and develops a negative charge. Since the anode has a positive charge and the cathode has a negative charge, the Ag+ ions formed by the anode are attracted to the cathode, therefore plating it with Ag.
Now that we are done with the explanations, I am now going to state the differences and similarities between the two types of cells
Similarities:
Both use redox reactions
The anode is the site of oxidation and the cathode is the site of reduction
Electrons flow through the wire from the anode to the cathode.
Differences:
Voltaic has a spontaneous chemical reaction, while the electrolytic cell is non-spontaneous.
A voltaic cell has a negative anode and a positive cathode, while in an electrolytic cell it is opposite.
Organic Chemistry:
Naming alcohol
- prefix = # of carbons
- # in the front shows the position of where the OH is
- ends in -ol
- an indicates single carbon bond; en indicates double;
E.g. 2-pentanol
5 carbons in the straight chain, all single bonds, OH is in the 2nd position
Naming Ethers:
- Put branches in order of increasing # of carbons.
- Name branches on each side of the Oxygen according to # of C.
- Add ether at the end of the name.
- Add -yl to the end of each branch name
E.g ethyl- propyl ether
2 carbons on one side of the oxygen and 3 carbons on the other side, all singly bonded.
Naming Organic Acids:
- Name ends with Acid
- prefix represents number of carbons.
- suffix for names is -oic
- an signals single bond and en signals a double bonded carbon.
E.g heptanoic acid
7 carbons singly bonded with a double bonded O and single bonded OH on the last carbon.
Naming Ketones:
- # represents the position of the double bonded Oxygen.
- Prefix for # of C.
- ends in -one.
Naming Aldehydes:
- Change the ending of parent chain to -al.
Naming Esters:
- Name the branch according to the # of carbons that does not contain the double bonded O.
- Name the main branch according to the # of carbons that contain the double bonded O.
- Branch goes first in name.
- Ends with -oate
good job =) =.=
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