C7 & 8 - Organic Chemistry & Chemical Analysis Flashcards
What is organis chemistry about?
Compounds that contain carbon. Hydrocarbons are the simplest organic compounds
What is an alkAne?
The simplest type of hydrocarbon, with single C-C bonds and therefore saturated (meaning they’re not very reactive). Every carbon atom has 4 single covelant bonds
What is the formula for an alkAne?
C H
n 2n+2
What does a homologous series mean?
It is a group of organic compounds that react in a similar way. AlkAnes and alkEnes are examples of this
What is crude oil?
A mixture of lots of different hydrocarbons, most of them being alkanes
Give the names for these first 4 alkanes:
a) C H4
b) C2 H6
c) C3 H8
d) C4 H10
e) C5 H12
a) Methane
b) Ethane
c) Propane
d) Butane
e) Pentane
When does complete combustion occur?
When there is plenty of oxygen
What type of bonds are in hydrocarbons?
Covelant bonds
As the hydrocarbon chain gets shorter:
a) It gets more/ less viscous (runny)
b) It gets more/ less volatile (lower/ higher boiling points)
c) It is more/ less flammable
a) more viscous (runny/ gloopy)
b) more volatile (lower boiling points)
c) more flammable
What are short hydrocarbon chains used more for?
“Bottled gases” - stored under pressure as liquids in bottles
Give the equation of complete combustion of hydrocarbons
hydrocarbon + oxygen - carbon dioxide + water (+energy)
What is oxidation?
During complete combustion of hydrocarbons, what gets oxidised?
The gain of oxygen
Both carbon and hydrogen from the hydrocarbon (forms cO2 and h2O)
Why are hydrocarbons used as fuels?
They release a lot of energy when the combust completely
Balance this equation then give the names:
CH4 + O2 – CO2 + H2O
What is this?
CH4 + 2O2 – CO2 + 2H2O
Methane + oxygen – carbon dioxide + water
Complete combustion of methane
What method is used to separate crude oil?
Fractional distillation
Talk about how crude oil is formed/
It is a fossil fuel, so takes a very long period of time to form.
The remains of plants and animals (mainly plankton) that died millions of years ago were buried in mud. With a high temperature and pressure, the remains turned into crude oil, which can be drilled up from the rocks where it’s found millions of years later
Is crude oil a renewable or non-renewable fuel?
Non-renewable fuel - it is finite as it is being used faster than it can be created
Give the method for fractional distillation of crude oil
1) The oil is heated until most of it has boiled into a gas. The gases enter a fractionating column, and the liquid part is drained off (bitumen)
2) There is a temperature gradient in the column - it’s hot at the bottom and gets cooler as it goes up
3) The longer hydrocarbons have high boiling points, so they condense back into liquids and drain out of the column early on (when they’re near the bottom) The shorter hydrocarbons have lower boiling points, so they condense and drain out much later on (when they’re near the top)
4) You end up with the crude oil mixture separated out into different fractions. Each fraction contains a mixture of hydrocarbons that all contain a similar amount of carbon atoms, so all have similar boiling points
What does LPG (Liquefied Petroleum Gas) contain?
Mostly propane and butane
Order these with has a higher boiling point, so becomes a liquid at the bottom of the tank first
a) Petrol
b) Diesel oil
c) Bitumen
d) LPG
e) Kerosene
f) Heavy fuel oil (heating oil, fuel oil or lubricating oil)
HIGHEST BP, BOTTOM OF COLUMN
c) Bitumen
f) Heavy fuel oil (heating oil, fuel oil or lubricating oil)
b) Diesel oil
e) Kerosene
a) Petrol
d) LPG (Liquefied Petroleum Gas)
How is crude oil used in modern life?
Provides the fuel for most modern transport - cars, trains, planes, many more.
Diesel oil, kerosene, heavy fuel oil and LPG all come from crude oil
What does the petrochemical industry use some of the hydrocarbons for?
As a feedstock to make new compounds to use such as polymers, solvents, lubricants and detergents
What are all the products you get crude oil from examples of?
Organic compounds - compounds containing carbon atoms.
What does cracking mean?
Why would people do it?
Splitting up long-chain hydrocarbons into smaller hydrocarbons.
Long-chain hydrocarbon chains are thick, gloopy liquids like tar which aren’t that useful whilst short chain hydrocarbons are more flammable so better as fuels, and are in high demand.
The longer alkane molecules produced in fractional distillation are turned into smaller & more useful ones
What is the main difference between alkanes and alkenes?
AlkEnes are a lot more reactive - they are non-saturated
What are alkenes used to make?
Polymers, so plastics.
They are used as a starting material when making lots of other compounds
Give the test for seeing if alkenes are present
By adding bromine water - when orange bromine water is added to an alkAne no reaction will occur and it will stay orange.
- when orange bromine water is added to an alkEne the bromine reacts with the alkene to make a colourless compound - so the bromine water is decolourised
Why do you get such a large variety of products from crude oil and organic compounds?
Because carbon atoms can bond together to form different groups called homologous series. These groups contain similar compounds with many properties in common.
What different ways are there to crack hydrocarbons?
Cracking is a thermal decomposition reaction - breaking molecules down by heating them
Heat long- chain hydrocarbons to vaporise them (turn them into a gas), then pass the vapour over a hot powedered aluminium oxide (catalyst). The long-chain molecules are split apart on the surface of the specks catalyst - this is catalytic cracking.
You can also crack them if you vaporise them, mix them with steam and then heat them to a very high temperature. This is steam cracking
What does decane crack into?
Octane + ethene (an alkene for making plastics)
Ethene is an alkane used for making plastics. True or false?
False - it is an alkEne for making plastics (double carbon bond, 4 hydrogen atoms)
What does pure mean?
Something that only contains one compound or one element throughout - not mixed with anything else
What does pure mean?
Something that only contains one compound or one element throughout - not mixed with anything else
Complete the sentence:
The boiling/ melting points tell you…
how pure a substance is
Complete the sentence:
The boiling/ melting points tell you…
how pure a substance is, as a chemically pure substance will boil/ melt at a specific temperature
How can you test the purity of a sample?
You can measure its melting/ boiling point and compare it to the melting/ boiling point of the pure version of that substance (found in a data book). The closer you measure the value to the real value, the more pure it is
What will impurities in a sample do when you try and melt it to find out how pure it is?
What about if you try and boil it?
Impurities will lower the melting point, and increase the melting range of the substance.
Impurities will increase the boiling point and may result in the sample boiling at a range of temperatures
What is the definition of a formulation?
Formulations are useful mixtures with a precise purpose that are made by following a precise formula/ recipe. Each component is present in a measured quantity, and contributes to the properties of the formulation so that it meets its required function
Give some examples of formulations
Paint, medicine, fertilisers
in everyday life, products, fuels, cosmetics, metal alloys and even food & drink
Talk about the functions of these components used in the formulation of paint:
a) Pigment
b) Solvent
c) Binder (resin)
d) Additives
a) Gives the paint colour, for example titanium oxide is used as a pigment in white paints
b) Used to dissolve the other components and alter the viscosity (runny)
c) Forms a film that holds the pigment in place after it has been painted on
d) Added to further change the physical and chemical properties of the paint
Depending on the purpose of the paint, the chemicals used and their amounts will be changed so the paint produced is right for the job
In what industry in particular are formulations important in?
The pharmceutical industry - by altering the formulation of a pill, chemists can make sure it delivers the drug to the correct parts of the body at the right concentration, that it’s consumable and has a long enough shelf life
What do the percentages on a product mean?
Shows you how much of a component is in that formulation.
What is chromatography?
An analytical method to separate dyes in a mixture, then identify the substances
What are the 2 phases in chromatography? What happens with these 2 phases?
1) A mobile phase - where the molecules can move. This is always as a liquid or a gas (the solvent e.g. ethanol or water)
2) A stationary phase - where the molecules can’t move. This can be a solid or a really thick liquid (often filter paper)
During the experiment, the substances in the sample constantly move between these phases - an equilibrium is formed between them
Chemicals that spend more time in the mobile phase during chromatography will move further through the stationary phase. True or false?
True
Complete the blanks: (for chromatography)
The components in a mixture will normally separate through the __________ phase, so long as all the components spend different amounts of ____ in the _____ phase. The number of spots may ______ in different ________ as the distribution of the chemical will change depending on the _______. A ____ substance will only ever form ___ spot in any solvent as there is only ___ substance in the sample
Stationary Time Mobile Change Solvents Solvent Pure One One
What does the amount of time the molecules in chromatography spend in each phase depend on?
How soluble they are in the solvent
How attracted they are to the paper
Molecules with a higher solubility in the solvent - which are attracted less to the paper - will spend more time in the mobile phase, and will be carried further up the paper
If molecules spend more time in the mobile phase, do they travel a lot or a little during paper chromatography?
A lot
How do you calculate the Rf value of each chemical in chromatography?
Distance travelled by solvent (A)
What does the Rf value of chromatography mean?
The ration between the dissolved substance (the solute) and the distance travelled by the solvent. The further through the stationary phase a substance moves, the larger the Rf value.
How do you find out if a certain substance is in a mixture in paper chromatography?
You test the pure substance alongside it, and compare the distances. If they have the same Rf value, then the certain substance is there
Say how you test for these common gases:
a) Chlorine
b) Oxygen
c) Carbon dioxide
d) Hydrogen
a) It bleaches damp litmus paper turning it white.
b) It will relight a glowing splint
c) Causes an aqueous solution of calcium hydroxide (or limewater) to become cloudy
d) When a lighted splint is held there, it will make a squeaky pop
Why may the litmus paper turn red at first when you’re testing for chorine gas?
Because a solution of chlorine is acidic
