find the oxidation state of a carbon in methane, carbon monoxide, carbon dioxide, CH2O, acetic acid, carbonic acid, methanol, and benzene (C6H6)
Rules for oxidation state.
http://www.chemteam.info/Redox/Redox.html
C in CH4,
H is +1 and there are 4 so total charge on 4 H is +4. Since the molecule is zero, C must be -4
C in benzene, C6H6
H is +1. 6*+1 = +6.
Since benzene is 0 charge, then 6 C must be -6 and EACH C must be -1 each.
To find the oxidation state of carbon in a molecule, you need to follow a few steps:
1. Identify the electronegativity difference between carbon and other elements in the molecule.
2. Assign the shared electrons to the more electronegative element.
3. Calculate the oxidation state of carbon based on the number of electrons it gains or loses.
Let's go through the molecules one by one:
1. Methane (CH4):
In methane, each hydrogen atom shares one electron with carbon using a single bond. Hydrogen is less electronegative than carbon, so all four electrons are assigned to carbon. Since carbon gains four electrons, its oxidation state is -4.
2. Carbon monoxide (CO):
In carbon monoxide, the oxygen atom is more electronegative than carbon. Oxygen and carbon share two electrons with a double bond. The shared electrons are assigned to oxygen since it is more electronegative. Carbon loses two electrons, so its oxidation state is +2.
3. Carbon dioxide (CO2):
In carbon dioxide, the oxygen atoms are again more electronegative than carbon. Each oxygen atom shares two electrons with carbon using double bonds. The shared electrons are assigned to oxygen. Carbon loses four electrons, so its oxidation state is +4.
4. CH2O (Formaldehyde):
In formaldehyde, the oxygen atom is more electronegative than carbon. Each hydrogen atom shares one electron with carbon, and the carbon-oxygen bond is a double bond with two shared electrons assigned to oxygen. Carbon loses two electrons, so its oxidation state is +2.
5. Acetic acid (CH3COOH):
In acetic acid, the oxygen atoms are again more electronegative than carbon. Hydrogen atoms share one electron each with carbon, and the carbon-oxygen bond is double between carbon and one oxygen. The other oxygen is connected by a single bond with one shared electron assigned to oxygen. Carbon loses two electrons, so its oxidation state is +2.
6. Carbonic acid (H2CO3):
In carbonic acid, the oxygen atoms are more electronegative than carbon. Hydrogen atoms share one electron each with carbon, and the carbon-oxygen bonds are double bonds with two shared electrons assigned to oxygen. Carbon loses four electrons, so its oxidation state is +4.
7. Methanol (CH3OH):
In methanol, the oxygen atom is more electronegative than carbon. Each hydrogen atom shares one electron with carbon, and the carbon-oxygen bond is a single bond with one shared electron assigned to oxygen. Carbon loses one electron, so its oxidation state is +1.
8. Benzene (C6H6):
In benzene, each hydrogen atom shares one electron with carbon using single bonds. All the carbon-carbon bonds in benzene are identical, and each carbon atom is equally electronegative compared to the others. Therefore, the oxidation state of each carbon atom is considered the same, and it is usually assigned as 0.
Remember that oxidation states are just a formal way to keep track of electron transfer, and they may not always represent the actual charge on the atom.