Developing fuels Flashcards
What is meant by organic chemistry
the study of the structure, properties, composition, reactions, and preparation of carbon-containing compounds.
How many bonds does each carbon atom typically form in an organic molecule?
4
What should the ‘full structural formula’ of a molecule look like? (e.g. pentane)
have bonds and elements shown
H H H H H
| | | | |
H-C-C-C-C-C-H
| | | | |
H H H H H
What should the ‘skeletal formula’ of a molecule look like? (e.g. pentane)
Only carbon bonds shown, Carbons are represented by ends
/\/\
What is the definition of a ‘hydrocarbon’ compound?
compound only made up on hydrogen and carbon atoms
What is the definition of a ‘saturated’ compound vs. an “unsaturated’ compound?
saturated compounds have no C=C bonds
What is the definition of an ‘aliphatic’ compound vs. an ‘aromatic’ compound?
aliphatic has no benzene rings
What structural features do all ‘alkanes’ have in common?
-only have single bonds
-hydrocarbon
What is the ‘general formula’ of an alkane?
CnH2n+2
What chemical test can be used to show that the cracking process has been successful?
Bromine water turns from orange to colourless
What effect does catalytic cracking have on a long chain alkane molecule?
- break a long chain alkane into shorter alkene(s) and an alkane
What is meant by a ‘sigma’ bond in a molecule
two of any orbital with an unbonded electron colliding head to head
What is meant by a ‘pi’ bond in a molecule
two p orbitals with an unbonded electron colliding side to side parallel with the internucli axis
In terms of sigma and pi bonds, what does a double covalent bond consist of?
a single sigma bond
What is the general definition of a catalyst?
a substance that is not used up that lowers the activation energy of a reaction by proving an alternative pathway
Which is stronger – a sigma bond or a pi bond? Explain.
sigma- on the internucli axis- stronger electrostatic forces of attraction- more energy to break
How can you tell from a balanced equation that something used as part of a process is probably a catalyst?
same on both sides of the equation
What is meant by a homogeneous catalyst?
catalyst that is in the same state as the reactants
What is meant by a heterogeneous catalyst?
catalyst that is a different state as the reactants
What are the steps in the mechanism by which a heterogeneous catalyst functions?
reactants bond and adsorb to the catalyst surface
Bonds in reactants weaken an break
Nee bonds form, creating the product
the product desorbes from the surface and diffuses away
How do a catalyst ‘poison’ decrease the effectiveness of a heterogeneous catalyst?
reacts with catalyst surface, blocking the reactants from adsorbing, reduces available for adsorption
catalyst reduces in activity
What chemical test can be used to show that the cracking process has been successful?
bromine water added goes from orange to colourless
what is the equation for the removal of CO and NO
2 CO(g) + 2 NO (g) —> 2CO2(g) + N2(g)
Explain the energy change in breaking bonds in terms of endothermic and exothermic processes
breaking bonds requires energy from surrounds, so is an endothermic process
forming bonds releases energy into surroundings, so is ab exothermic process
Explain what makes a reaction endo/exothermic
if the enthalpy change is positive, and the surrounding temperature has decrease, this is because the energy required to break bonds is higher than the energy released by forming bonds and the reaction is endothermic.
