C7 organic chemistry Flashcards
What is the word equation for complete combustion?
fuel + oxygen -> carbon dioxide + water
What is the word equation for incomplete combustion?
fuel + oxygen -> carbon monoxide + water + carbon (soot)
Why should sulfur be removed from petrol?
Sulfur produces sulfur dioxide which can cause acid rain
Describe a test for ethene and give the result.
Mix with bromine water. Turns orange to colourless
Explain how carbon monoxide is produced.
Incomplete combustion due to a limited supply of oxygen
How can different forms of poly(ethene) be produced from ethene?
Using different reaction conditions (like temperature and pressure)
Why does a thermosetting polymer not melt and a thermosoftening polymer melt?
- It has crosslinks between chains which are held in position so chains can’t slide over each other
- It has no crosslinks and weak intermolecular forces between chains which require little energy to overcome
Name two naturally occurring polymers produced from glucose
- Starch
- Cellulose
Compare addition and condensation polymerisation (2)
- Addition only one product condensation also small molecules like water
- Addition produced from one monomer (alkenes) wheareas condensation produced from two different monomers with two of the same functional groups (‘di’), aren’t alkenes
Compare ethane with ethene
You should refer to:
* their structure and bonding
* their reactions
Structure and bonding:
- Both are hydrocarbons containing carbon and hydrogen atoms only
- Ethane contains a single C-C bond whereas ethene contains a double C=C bond
- Ethane has 6 hydrogen atoms whereas ethene only has 4
Reactions:
- Ethene is more reactive
- Ethene can react with halogens, hydrogen and water whereas ethane can’t
- Both react with oxygen in complete combustion to produce water and carbon dioxide, ethene more likely to undergo incomplete combustion and burn with a smoky flame as some carbon particles unburnt
Describe how ethanol is produced from sugar solution
By fermentation: add yeast in anaerobic and warm conditions (30 degrees)
What type of substance reacts with an alcohol to produce a carboxylic acid?
Oxidising agent
Why does limewater turn cloudy?
Carbon dioxide present so precipitate formed
Describe the differences between cracking and distillation (2)
- Cracking (can) involve a catalyst, distillation doesn’t
- Distillation does not involve a chemical change (only physical) but cracking does
What are the advantages and disadvantages of poly(ethene)?
A:
can be recycled
durable
D:
not biodegradable
finite
What functional groups make amino acids?
NH2 (amine) and -COOH (carboxylic acid)
Why do larger hydrocarbons condense lower in a fractionating column?
Higher boiling point so condense at the bottom of the column as it has a higher temperature
Why are larger hydrocarbons not used as fuels? (3)
Too viscous
B.p too high
Not as flammable
Explain why large hydrocarbon molecules are cracked to produce smaller hydrocarbon molecules
Smaller hydrocarbons have a higher demand as they are more useful as fuels and are used to make alkenes which are used to produce polymers
Describe how crude oil is separated into fractions
Crude oil is heated and evaporates up the fractionating column with a temperature gradient (cooler at the top and hotter at the bottom) so fractions condense at different levels based on their b.p
Describe how cracking is carried out
Heat and so vaporise the hydrocarbon and pass over a (hot) catalyst (aluminium oxide)
Why can alkenes form polymers?
They have a double C=C bond which can be broken so alkenes can bond to other molecules
Describe how ethene forms poly(ethene)
Double C=C bond is broken and many ethene molecules (monomers) join to form a large molecule
Why do alkenes have different chemical properties from alkanes?
Alkenes are unsaturated with different homologous series to alkanes as they have double C=C bonds whereas alkanes have only single C-C bonds
What ester is made from ethanoic acid and ethanol in the presence of a (strong) acid catalyst?
ethyl ethanoate
Why in addition polymerisation does the repeating unit have the same atoms as the monomer?
No other molecule is formed in the reaction
Describe the structure of a DNA molecule
Two polymer chains made from four different monomers called nucleotides (A T G C) in the form of a double helix
What type of monomer is the naturally occurring polymer protein made of?
Different amino acids combined in the same chain
Why may graphs with one quadrant not be suitable to show negative results?
Result wouldn’t fit on the graph
What happens in addition reactions?
Double bond breaks to form two extra bonds
How do you know ethanoic acid is a weak acid?
It has a reversible reaction so it doesn’t completely ionise into H+ ions - it partially ionises in aqueous solution
What is the formula for propanoic acid?
CH3CH2COOH
What gas is produced when sodium is added to ethanol?
Hydrogen
Explain what happens to the mass of a flask and contents when ethnic acid and zinc carbonate react in an open flask
Mass decreases as carbon dioxide gas is produced which escapes from the open flask
What polymers are biodegradable?
Condensation polymers
What type of reaction is cracking and explain it
Splitting large chain hydrocarbons into smaller chain hydrocarbons + alkenes by heating (thermal decomposition reaction)
Describe the 3 addition reactions with alkenes
HYDROGENATION
- produces an alkane from a nickel catalyst
HYDRATION
- produces an alcohol when water is heated to steam and phosphoric acid catalyst present
HALOGENATION
- produces a dihaloalkane
Explain how ethanol is made from glucose and the name of the process
ferment(ation)
add yeast
in anaerobic (conditions)
or
warm
in a fermentor
