Inorganic chemistry - study of carbon compounds Flashcards
Define a displayed formula
Shows the relative spacing and placing of atoms and the number of bonds between them
Define an expanded formula
Gives the minimal detail using conventional groups for a non-confusing structure
Define an empirical formula
Shows the simplest whole number ratio of atoms in a molecule
Define a molecular formula
It gives the exact number of atoms of each element in the compound but doesn’t tell you about the bonding
Define a structural formula
Shows the arrangement of atoms in a molecule of a compound but not all the bonds between them ( only certain bonds)
Define a skeletal formula
A diagram representation of an organic compound in which lines represent bonds between atoms and atoms are represented by their chemical symbol.
* if no symbol is present assume tat hydrogens are found at the end of the line
Define general formula
Represents the composition of any member of an entire class of compounds ie alkanes have general formula CNH2N + 2
What is the general formula for alkanes
CNH2N + 2
What is the general formula for alkenes ?
CNH2N
What is the general formula for haloalkanes ?
CNH2N + 1
What is the general formula for a carboxylic acid ?
RCOOH
where R = CNH2N + 1
What is the general formula for alcohols ?
CNH2N + 1 OH
What is the general formula for a ketone ?
RCOR
where R = CNH2N + 1
Name the first 10 alkanes
methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane
mneumonic to remember - most eagles play basketball professionally however hamsters only nibble donuts
What is the symbol and charge for an ammonium ion ?
NH4 +
What is the symbol and charge for a nickel ion ?
Ni2+
What is the symbol and charge for a nitrate ion ?
NO3 - ( 3 oxygens)
What is the symbol and charge for a nitrite ion ?
NO2 - ( 2 oxygens)
What is the symbol and charge for a carbonate ion ?
CO3 2-
What is the symbol and charge for a sulphate ion ?
SO4 2-
What is the symbol and charge for a sulphide ion ?
S 2-
What is the symbol and charge for a sulphite ion ?
SO3 2-
What is the symbol and charge for a nitride ion ?
N 3-
What is the symbol and charge for a phosphate ion ?
PO4 3-
As alkane chain gets longer what properties develop ?
more viscous, harder to ignite and higher boiling point
If the C chain is more branched what does this mean
Lower boiling point due to weaker Vanderwall forces ( intermolecular)
What is cracking and what are the two different types of cracking ?
- cracking is used to break up large hydrocarbons into smaller ones
- two types are thermal and catalytic cracking
What are the conditions needed for thermal cracking
900 C, 70 atm of pressure and the products are alkanes
What are the conditions needed for catalytic cracking
450 C, 1-2 atm of pressure, zeolites ( catalysts) and products are branched alkanes
Why are alkanes good fuels
Burn readily in the presence of oxygen, very exothermic reaction
What are the products of complete vs incomplete combustion
complete combustion produces carbon dioxide and water while incomplete combustion produces carbon monoxide and carbon ( soot)
What problem does CO cause
toxic, binds to cells better than O2, also colourless and odourless
to prevent its production, good oxygen supply when burning fuels
What problem does soot form ?
blackens buildings, causes respiratory issues and global dimming
To prevent this, good supply of o2 when burning fuels
What problem is caused by NO2 and SO2 ?
acid rain which damages trees, harms aquatic life
this can be prevented by removing sulfur from fuel before burning and using catalytic converters in cars
What problem is caused by unburnt hydrocarbons ?
fuel wastage, engines should be well tuned and have a good o2 supply
Why are alkanes very unreactive ?
they are not polar molecules and also have very strong bonds which requires a lot of energy to break
What is a free radical
Any chemical species with an unpaired electron
What are the three stages of a free radical reaction ?
Initiation, propagation, termination
Describe the stages of reaction between methane and bromine
initiation - UV light shone onto BR2 which has a single covalent bond consisting of a pair of electrons. one electron goes to each Br atom. Teo Br free radicals are made
propagation- bromine free radical reacts with CH4. Nicks a H atom from methane and an electron, forming HBR and a methyl free radical. methyl free radical reacts with Br molecule producing bromomethane and BR free radical
termination - two free radicals react to form a stable molecule one with no unpaired electrons ie two Br radicals react to form a Br molecule
What is the problem with free radical substitution of alkanes
many side products are formed
What is an isomer ?
A structure with the same molecular formula but at least one different chemical/ physical property
Longer isomers have what
Higher boiling points
What is a structural isomer ?
Same molecular formula but a different structure
What are the three types of structural isomers
chain isomers - different carbon chain
position isomers - different position of functional group
functional group isomers - different functional group
What are stereoisomers ?
molecules with same structural formula but different spatial arrangement of atoms ( EZ isomers)
What are the two types of stereoisomers
- optical isomers have two molecules which are non-superimposable mirror images of each other. Means you can’t slide one molecule exactly over the other because one would always be pointing in wrong direction
- geometric isomers: in gemoeric isomers functional groups cannot freely rotate around chemical bond, generally because of a carbon carbon double bound
What is cis trans ?
naming system for geometrical isomers . carbon atoms on double bond must be attached to two different groups and at least one of these groups mus teb the same on both C atoms of the double bond
Cis isomer
the groups are on the same side of the molecule
Trans isomer
the groups are on opposite sides of the molecule
Z isomer
the groups are on the same side of the molecule
E isomer
the groups are on different sides of the molecule
E/Z system
- another naming system for isomers
- works even if the carbon atoms on either side of double bond are attached to more than 2 groups
- to use this system establish which atoms which groups have priority on the left and right hand side of double bond
- higher priority based on higher atomic number
- then used higher priority groups to decide which is E and which is Z isomer
mass of an ion in kg
(mass number x 10^-3) / avogadro’s constant
how to deduce the group of an element by looking at successive ionisation energies
- look for biggest jump in energy
- whatever two numbers this jump is between ie 5th and 6th ionisation energies, first number represents the valence shell and the second number represents inner shell.
the large jump in ionisation energy shows that the shell is inner because there is a larger attraction between the electron and nucleus than with the valence shell.
What are the two important formulas to remember for time of flight calculations?
kinetic energy = 1/2 x m x v^2
v = d/t
