Organics Flashcards
Crude oil
A mixture of unrefined hydrocarbons
How is crude oil formed?
- Millions of years ago, huge numbers of plankton died and fell to the bottom of the sea. Their remains were covered by mud
- As the mud was buried further, and the temperature and pressure increased, it started to change into rock. The dead plankton were slowly cooked, changing gradually into oil
- The oil rose due to pressure from below, getting trapped under impermeable rocks, such as those in the sedimentary layer of the Earth’s crust
Hydrocarbon
A compound made up of carbon and hydrogen atoms only
How are the following properties affected as the number of carbon atoms in a hydrocarbon increases:
- Boiling point
- Darkness of hydrocarbon
- Viscosity
- Flammability
- Smokiness of flame
Boiling point: increases Darkness: increases Viscosity: increases Flammability: decreases Smokiness: increases
Fractional distillation
Used to separate hydrocarbons of different sizes into fractions
How does fractional distillation work? (4 points)
- All of the crude oil is heated and vaporised
- It is then fed into a fractionating tower
- This is hot at the bottom and cold at the top
- The hydrocarbons rise up the tower and condense at different points due to their differing boiling points
- As each fraction contains a mixture of hydrocarbons, the boiling point of each fraction is a range
Why is the boiling point of each fraction a range?
Each fraction contains a mixture of different hydrocarbons
Order the following six in order of increasing boiling point and give a use for each: Bitumen Gasoline Refinery gases Diesel oil Kerosene Fuel oil
- Refinery gases: everyday cooking
- Gasoline: petrol
- Kerosene: jet fuel
- Diesel oil: diesel fuel
- Fuel oil: ship fuel
- Bitumen: road tar
Combustion reaction
A chemical reaction where a compound and an oxidant react to produce heat and a new product
Fuel
A substance that reacts with oxygen to release useful energy, mostly as heat energy
What are the two kinds of combustion?
- Incomplete
2. Complete
Complete combustion:
- When does it occur?
- General word equation
- When there is a steady supply of oxygen
2. Hydrocarbon + oxygen → carbon dioxide + water
Incomplete combustion:
- When does it occur?
- General word equation
- When the supply of oxygen is poor
2. Hydrocarbon + oxygen → carbon monoxide + carbon + water
How can the occurrence of incomplete combustion lead to death?
Carbon monoxide is poisonous. It can be fatal if inhaled, as it cuts off oxygen supply by binding irreversibly to the haemoglobin in red blood cells
Three common air pollutants and how they are formed
- Carbon monoxide: incomplete combustion of the fuel in car engines
- Nitrogen oxides: formed from the heat and pressure found in a car engine
- Sulphur dioxide: sulphur impurities in fuels burn
How are nitrogen oxides formed?
The energy from the spark plug in a car is sufficient for the usually unreactive nitrogen gas in air to react with oxygen
What hazards does the emission of nitrogen oxides lead to?
- They react with other pollutants in sunlight to form a photochemical smog, causing breathing difficulties
- Acid rain
What hazard does the emission of sulphur dioxide lead to?
Acid rain
What effects does acid rain have on the environment?
- Kills plants
- Poisons aquatic life
- Erodes stonework e.g. limestone
- Corrodes metals
Steps for experiment to separate crude oil into fractions
- Pour crude oil into a boiling tube
- Fit a thermometer into the boiling tube
- Connect a delivery tube to the boiling tube
- Heat the crude oil gently at first, then more strongly
- Collect each fraction in a different test tube
Which two methods can you use to confirm that water is formed during complete combustion?
- Cobalt chloride paper should turn pink
2. Anhydrous copper sulphate should turn blue
How can you confirm that carbon dioxide is formed during complete combustion?
Limewater should turn cloudy
Why are shorter hydrocarbons more useful?
- More flammable
- Burn for longer
- Less smoky i.e. cleaner
Catalytic cracking
The process by which longer chain alkanes are broken down into more useful products