SC22a - What is a hydrocarbon?
A molecular compound containing only hydrogen and carbon atoms
SC22a - What is the functional group of an alkane?
Trick question. They have no functional group
SC22a - What is the general formula of an alkane?
SC22a - What are the first four prefixes for all the homologus serieses?
- Meth- (Don't do drugs)
SC22a - According to the IUPAC, how are hydrocarbons (and many other molecule types) named?
- Prefix showing its number (e.g. Meth- is 1)
- Suffix showing its homologous series (e.g -ane is alkane)
SC22a - Why is an alkane saturated?
It only contains single bonds between carbon bonds meaning it can't open out and bond to more atoms
SC22a - What are the displayed and molecular formulae of the first four alkanes?
SC22a - What is a functional group?
The part of a molecule that identifieis it with its specific functional group and is responsible for its chemical properties
(e.g all carboxylic acids have COOH )
SC22a - What is the functional group of an alkene?
All alkenes contain one double covalent bond between two carbon atoms
SC22a - What is the general formula of an alkene?
SC22a - Why is there no 'methene' ?
A meth- alkene would have 1 carbon atom but to be an alkene, it would need a double bond between carbons, which can't happen, unless there are 2+ carbon atoms
SC22a - Why is an alkene unsaturated?
It contains a double covalent bond between two carbon atoms, meaning that the bond can be opened out and another atom can bond to it.
SC22a - What are the molecular and displayed formula of the first 3 alkenes (remember there isn't a 'methene')
SC22a - What is an isomer?
The same molecule with their functional group placed in different places.
e.g. below is but-1-ene (as the group is in it's first possible position) and but-2-ene (with the group in the second position)
SC22a - Why are there no isomers of ethene and propene?
- Ethene only has 2 carbon atoms and so the double bond can only be in one place
- Propene has 3 carbon atoms and so the double bonds can be in 2 places however, positioning them in these two places would make reflections of the same molecule
SC22b - How do alkanes and alkenes react in combustion?
- When heated up sufficiently, hydrocarbons will oxidise, and combust, reacting with the oxygen in the air and releasing energy
- When sufficient oxygen is present, all the hydrocarbon will oxidise (complete combustion)
- Hydrocarbon + Oxygen → Carbon dioxide + water
- When there is a lack of oxygen, not all of the hydrocarbon will oxidise (incomplete combustion) Carbon monoxide and/or carbon aswell, instead of just carbon dioxide
- Hydrocarbon + Oxygen → Carbon dioxide + water
SC22b - How can you tell if a chemical is an alkene or an alkane?
- When placed in and mixed with bromine water, an alkane won't react and no change will be observed
- However, the double bond in an alkene, will open out and react with the bromine water taking it out of the water and it goes from orange-brown to colourless
SC22b - What colour is bromine water?
SC22b - What is an addition reaction
When more than one reactant reacts to form a larger product and no other products
SC22b - What is the word equation for the addition reaction between ethene and bromine water?
Ethene + Bromine water → 1,2 dibromoethane
(Don't know if this is required knowledge)
SC23a - What are the uses of ethanol?
- Alcoholic beverages
- Fuel for vehicles
- Material in raw industry
SC23a - What is ethanol made from?
- Sugars. These are small soluble substances that belong to a group called carbohydrates
- Seeds contain a carb called starch (a long polymer).
- Germinating seeds allows enzymes to break down the starch into sugars
- Fermentation uses enzymes in yeast to turn the sugars into ethanol
SC23a - What plants are used to make different alcoholic beverages?
- Beer - Barley seeds
- Wine - Grapes
- Whisky - Barley seeds
- Vodka - Wheat seeds
SC23a - Describe the fermentation process of ethanol
- Glucose → Ethanol + Carbon dioxide
- Yeast containing enzymes that will turn the glucose solution into ethanol
- Heat source keeps the solution at the optimum temperature of around 25 C
- Air lock lets out carbon dioxide, but doesn't let any oxygen in, allowing anaerobic respiration to occur
SC23a - What is the problem with the fermentation process and how is this overcome?
Only alcohol of 15% concentration can be produced (or else the yeast enzymes will be killed). So, fractional distillation is used to obtain high concentrations of alcohol.
Ethanol's b.p. of 78 C is less than water and so it evapourates first and condenses into a distillate of high conc. ethanol
SC23b - What is an organic compound?
A compound with a central framework of carbon atoms but with hydrogen and other atoms attached
SC23b - What is the functional group of the alcohols homologous series?
-OH atoms on the end of the compound
SC23b - What is the general formula of alcohols?
SC22a - What are the first four alkanes?
- -ane is prefix
SC22a - What are the first three alkenes?