SC22 & SC23 & SC24 - Hydrocarbons / Alcohols and Carboxylic Acids / Polymers Flashcards
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?
CnH2n+2
SC22a - What are the first four prefixes for all the homologus series?
- Meth- (Don’t do drugs)
- Eth-
- Prop-
- But-
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?
CnH2n
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
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?
Orange-brown
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?
CnH2n+1
SC22a - What are the first four alkanes?
- Methane
- Ethane
- Propane
- Butane
- -ane is prefix
SC22a - What are the first three alkenes?
- Ethene
- Propene
- Butene
- -ene is prefix
SC23b - What are the first four alcohols?
- Methanol
- Ethanol
- Propanol
- Butanol
- -anol is prefix
SC23c - What are the first four carboxylic acids?
- Methanoic acid
- Ethanoic acid
- Propanoic acid
- Butanoic acid
- -anoic acid is prefix
SC23b - What is the displayed and molecular formula of the first four alcohols
SC23b - What are the chemical properties of the alcohols?
- Produce carbon dioxide + water during complete combustion
- Can be oxidised to produce carboxylic acids
- React with reactive metals and produces hydrogen (among other products)
SC23b - What is the trend of reactivity for alcohols?
The longer the chain, the less vigorously they will react (for example less bubble produced when sodium is added)
SC23b - What are some uses of alcohols?
- Medical products
- Fuels
- Varnishes
- Cosmetics
SC23b - Describe the trend in energy stored per Litre for alcohols
Longer chains store more energy per litre, making them more effective fuels
SC23b - What is so advantageous about alcohol fuel?
They can be made from renewable sources such as fermenting plant cellulose using bacteria. (Currently methanol and ethanol fuels are being used)
SC23c - Why does wine turn into vinegar when left out?
The ethanol oxidises and turns into ethanoic acid (a type of vinegar)
SC23c - Describe the process of the oxidisation of an alcohol
- The Oxygen molecule from the air collides with the functional group of the alcohol
- Two hydrogen molecules are ‘knocked off’ and bond with an oxygen to form water
- Meanwhile the other oxygen bonds to the carbon forming a carboxylic acid
SC23c - What is the functional group of a carboxylic acid?
-COOH at the end
SC23c - What is the displayed and molecular formula of the first four carboxylic acids?
SC23c - What is the general formula of carboxylic acids?
CnH2n+1COOH
[Ok real talk guys. The above general formula is the one you need to know. However, unlike in other general formulas, the ‘n’ value isn’t the number in the series (idk what it is). So if you want a general formula based off number in series, Cn-1H2n-1COOH but if they ever ask in the exam what the general formula, it is the top one as that is the spec one]
SC23c - What are oxidising agents and why are they used?
- The natural process of oxidisation of an alcohol is time consuming and uncontrollable.
- Instead, reacting an alcohol with an compound that contains oxygen is more effective.
e.g Propanol + (hot) copper oxide → Propanoic acid + Water + Copper
SC23c - What are the chemical properties of carboxylic acids?
- Form solutions with pH less than 7 (if soluble)
- React with metals to from salt and hydrogen
- React with bases to form salt and water
- React with carbonates to form salt water and carbon dioxide
SC23c - What gives carboxylic acids their acidity?
The -COOH group has a H+ ion which makes it acidic
SC23c - How can vinegar be used to test for chalk/limestone?
Chalk/limestone are carbonates and so when vinegar is added, the ethanoic acid will fizz due the presence of carbon dioxide produced from the reaction
SC23c - Describe the trend in acidity of carboxylic acids
The longer the chain the less acidic (higher pH)
SC24a - What are plastics made from?
Polymers
SC24a - What is a polymer?
A long molecule made up of lots of tiny molecules called monomers
SC24a - What is polymerisation?
The process by which many monomers are joined together to form a polymer
SC24a - What is special about the relative atomic mass of polymers?
They can be very large due to having millions of molecules. As they can be any lengths, they are never given
SC24a - What is addition polymerisation?
When many of the same monomer are added together to form one polymer and no other products
SC24a - Describe the addition polymerisation of ethene into poly(ethene)
SC24a - What is the repeating unit of a polymerisation equation?
It shows how the monomer has changed and how it repeats throughout the polymer chain
SC24a - What is a synthetic polymer?
One manufactured in a lab/factory
SC24a - What are some examples of naturally occurring polymers?
- Starch (made of glucose)
- Protein (made of amino acids)
- DNA (made from nucelotides)
SC24b - How are polymers named?
Poly(name of monomer)
SC24b - Why can alkenes be used to make polymers?
They contain a double carbon bond that can be opened out to bond to more monomers
SC24b - What is key to remember when drawing repeating units?
Make sure the bond lines go through the brackets to show that it can continue to bond
SC24b - Properties and uses of Poly(ethene)
- Common name: Polythene
- Properties: Flexible, cheap
- Uses: Plastic bags, cling film
SC24b - Properties and uses of Poly(propene)
- Common name: polypropylene (wtf is the common name longer)
- Properties: Flexible, shatter resistant
- Uses: Buckets and bowls, ropes
SC24b - Properties and uses of Poly(chloroethene)
- Common names: polyvinyl chloride PVC
- Properties: Tough, good insulator
- Uses: Pipes, window frames
SC24b - Properties and uses of Poly(tetrafluorene)
- Common names: PTFE, Teflontm
- Properties: Tough, slippery
- Uses: Burette taps, non-stick coating
SC24c - What is a polyester?
A synthetic polymer made by condensation polymerisation. It contains many ester links
SC24c - What is the functional group of an ester?
SC24c - How are esters formed?
- When a carboxylic acid is reacted with an alcohol
Carboxylic acid + alcohol → ester + water
SC24c - Why is an ester-creating reaction considered a condensation reaction?
Water is produced
SC24c - How would ethanoic acid and ethanol react to form an ester?
The -OH from the ethanoic acid and the H from the ethanol will break off and react to form water. Then, the C on the acid will bond with the O from the alcohol
SC24c - What is required to form a polyester?
Each monomer has a functional group on BOTH sides
e.g. below is ethanoic acid and ethanol
SC24c - What will a polymer equation for the condensation polymerisation of ethanoic acid and ethanol?
This process is something that should be practiced as you need to practice drawing it out
SC24d - What is the problem with the process to make synthetic polymers?
They are obtained from crude oil which is a non-renewable finite resource and will eventually run out
SC24d - What does biodegradable mean?
It can rot as mircrobes can break it down
SC24d - What are the pros and cons of synthetic polymers being non-biodegradable?
+ They can be used for a long time
- They don’t rot when thrown away
SC24d - What are the pros and cons of incinerating plastic rubbish?
+ Takes up less space
+ Energy released can be used to generate electricity
- Produces Carbon dioxide (GH gas)
- Some plastics produce toxic substances when burnt (these can be removed but forms toxic ash which needs to be disposed)
SC24d - How can we reduce the amount of waste going to incinerators and landfill sites?
Re-using and recycling materials
SC24d - Describe the process of recycling polymers
- Collection (kerbside or recycle points)
- Sorting (can be expensive and time consuming)
- Disposal of un-recyclable wast to landfill sites
- Clean polymers and grind to chippings
- Purify chippings
- Melt and remould chippings
SC24d - How is the sorting process of recycling made easier?
Labels for each type of polymer
