11 - Organic Chemistry Flashcards
Why do fuels release energy?
Because combustion is exothermic. Activation energy is needed to break the bonds, which requires energy and is an endothermic process. The enthalpy of these bonds broken is not as high as the enthalpy of the bonds formed, which is exothermic. This means we have a negative enthalpy change (overall energy release to the surroundings).
Which fuel is the most effective between wood, ethanol or wax
- Which one releases more energy?
- Which one lasts longer?
Ethanol releases most energy (more power)
Wax lasts longer (more Joules per gram)
What is the general formula for the Alkene family
CnH2n
What is the general formula for the Alcohol family
Cn H2n+1OH
What is the general formula for the Alkane family
CnH2n+2
State 3 members of the Alkane family
CH4 - Methane (single carbon bond)
C2H6 - Ethane (idem)
C3H8 - Propane
State 2 members of the alcohol family
CH3OH - Methanol
C2H5OH - Ethanol
(they ends in OH)
How do molecules of Alkane look like ?
Chains of carbon surrounded by hydrogens
How do molecules of Alkene look like ?
A chain of carbons with one double Bond surrounded by hydrogens
How do molecules of Alcohol look like ?
A chain of carbons connected with an oxygen and a hydrogen at the end the rest is surrounded by hydrogens
What is in crude oil?
Mostly liquid alkanes
Hexane and above are liquid
Which molecules make up natural gases
80% is CH4 - Methane (1 carbon)
20% is - C2H6 - Ethane (2carbon)
- C3H8 - propane (3 carbon)
- C4H10 - Butane (4 carbon)
What is the general formula for alkane gas molecules
Cn H2n+2
Def. fuel
A substance that when burnt completely in oxygen releases heat energy (and forms waste products in the form of oxides)
What waste products do you get from combusting Carbon?
CO2
What waste products do you get from combusting Hydrogen?
H2O
What waste products do you get from combusting Propane?
CO2 + H2O
What is smoke and when is it formed?
Smoke is particles of carbon and is formed instead of Carbon dioxide by an insufficiency of oxygen to react with during combustion. Carbon monoxide can also be formed.
What is smoke and when is it formed?
Smoke is particles of carbon and is formed instead of Carbon dioxide by an insufficiency of oxygen to react with during combustion. Carbon monoxide can also be formed.
What is in crude oil/petroleum?
Alkanes
What is a fossil fuel?
A fuel made from dead organisms that have fossilised over time
What temperature is crude oil heated to in fractional distillation?
350 Degrees Celcius
How does fractional distillation separate crude oil?
The larger the molecules (alkane chains) are, the stronger intermolecular forces they have. This means they have a higher boiling point.
The smaller the molecules are, the weaker intermolecular forces they have. This means they have a lower boiling point.
The molecules with a lower boiling point move higher through the fractionating column before condensing, while substances with a highest boiling point will condense quickly.
What fractions are formed during the distillation of crude oil, and what are their purposes?
From smallest to largest
- Bottled/Refinery gas - miscelaneous
- Gasoline - Cars
- Naphta - Experiments
- Kerosene - Planes
- Diesel oil - Cars, lorries, buses
- Fuel oil - Ships, power stations
- Bitumen - Roads and roofs
How does fractional distillation of air work?
Air is cooled to -200 degrees celcius.
Carbon dioxide freezes and is removed. The other gases condense.
The liquid is distillated through the fractionating column, seperating Nitrogen, Argon, Oxygen and Krypton.
Def. Organic Compounds
Compounds made from carbon and hydrgen, and possibly other non-metals
Def. Homologous series
A family of similar compounds with similar chemical properties due to the presence of the same functional group
Def. Functional group
An atom or group of atoms that determine the chemical propertiesof a homologous series
What are the characteristcs of homologous series?
- They have the same functional group
- They have the same general formula
- They differ from one member to the next by one CH2 unit
- They display a trend in chemical properties
- They have similar chemical properties
What s the functional group of alkanes?
CC single bond
What is the functional group of alkenes?
CC double bond
Def. Isomer
Compounds that have the same molecular formula but different structural formula and arrangement of atoms
Def. Saturated hydrocarbon
Hydrocarbons in which all CC bonds are single bonds