Organic chemistry Flashcards
What are hydrocarbons?
Molecules that only contain hydrogen and carbon
What are alkanes called?
A homologous series
What are the first 4 alkanes going from smallest to biggest?
Methane (1 carbon), ethane (2 carbons), propane (3 carbons), butane (4 carbons)
What’s the general formula for alkanes?
CnH2n+2
Are alkanes saturated or unsaturated and what does this mean?
Saturated, meaning they only contain single bonds
What is crude oil?
A mixture of hydrocarbons
How is crude oil formed?
From the remains of dead plants and animals that died millions of years ago and over time with high temperature and pressure have turned into crude oil
What are the properties of short chain hydrocarbons?
Lower boiling points, volatile, runny, flammable
What are the properties of long chain hydrocarbons?
Higher boiling points, not volatile, viscous, not flammable
What separates crude oil and how does it work?
Fractional distillation - separates the oil into fractions based on their boiling points that have similar numbers of carbon atoms in them
The crude oil is heated and evaporates into a vapour that condenses at different temperatures because of their different boiling points (the fractionation column is cooler at the top and hotter at the bottom)
What is the word equation for burning hydrocarbons?
Methane + oxygen –> carbon dioxide + water
CH4 + 2O2 –> CO2 + 2H2O
What is the equation for incomplete combustion?
CH4 + 1½O2 –> CO + 2H2O
What do you use to test for carbon dioxide?
Lime water - it will change from clear to cloudy
What do you use to test for water?
Cobalt chloride paper - it will change from blue to pink
What is cracking?
The process of breaking down long chain hydrocarbons into short chain hydrocarbons
What are the two types of cracking and how do they work?
Catalytic cracking - the hydrocarbons are heated at a high temperature to vaporise them and then passed over a hot catalyst
Steam cracking - the hydrocarbons are heated at a high temperatures to vaporise and then mixed with steam at a high temperature
What is the functional group for alkenes?
C=C
Are alkenes saturated or unsaturated and what does this mean?
Unsaturated, meaning they contain at least one carbon double bond
What is the general formula for alkenes?
CnH2n
What are the first four alkenes going from smallest to biggest?
Ethene (2 carbons), propene (3 carbons), butene (4 carbons), pentene (5 carbons)
What is the functional group of alcohol?
OH
What two methods are used to produce alcohol and how do they work?
Hydration of ethene - ethene from crude oil is reacted with steam to produce ethanol (the process is pure and fast)
Fermentation of sugars - yeast is added to a source of sugar which is dissolved in water; temperature of around 30-40°C and air is kept out of the mixture (the product is impure and must be distilled to produce pure ethanol and the process takes a lot longer)
What are the first 4 alcohols going from smallest to biggest?
Methanol (1 carbon), ethanol (2 carbons), propenol (3 carbons), butanol (4 carbons)
What is the word equation for alcohol reacting with sodium?
Alcohol + sodium –> sodium alkoxide + hydrogen
What is the functional group of carboxylic acids?
COOH
What are the first four carboxylic acids going from smallest to biggest?
Methanoic acid (1 carbon), ethanoic acid (2 carbons), propanoic acid (3 carbons), butanoic acid (4 carbons)
Why are carboxylic acids weak?
Because they only partially ionise in solution
What is the word equation for carboxylic acids reacting with carbonates (starting with ethanoic acid + sodium carbonate)?
Ethanoic acid + sodium carbonate –> sodium ethanoate + carbon dioxide + water
What is the word equation for carboxylic acids reacting with alcohol?
Carboxylic acid + alcohol <–> ester + water
What are some uses of esters?
Perfumes, flavourings, solvents
What are the properties of high density polyethene?
Uses a catalyst at 50°C and a lower pressure, made up of straighter molecules, stronger than low density polyethene, makes up plastics that are more dense, rigid and harder to melt
What are the properties of low density polyethene?
Uses a temperature of 200°C and higher pressure, the polymer chains are branched out and can’t pack closely together, weaker than high density polyethene, makes up plastics that are light, soft and easier to melt
What is thermosoftening plastic?
Plastic that can be melted and remoulded repeatedly
What is thermosetting plastic?
Plastic that keeps its shape once heated and molded even if its heated again
Why do thermosetting plastics keep their shape?
Because the monomers form covalent bonds between polymer chains when they are first heated
What are some naturally occurring polymers?
Amino acids, DNA, cellulose, starch
How can you test for the presence of an alkene?
Reacting it with bromine water, it will decolourise the bromine water from orange-yellow if the alkene is present
