(P2)Fuels Flashcards
What type of bonds do hydrocarbons have?
Covalent bonds
What is crude oil?
A fossil fuel which consists of a mixture of hydrocarbons. It is a finite resource and takes millions of years to form
Why can crude oil be separated using fractional distillation?
Because the hydrocarbons have different boiling points
What happens to the boiling point of a hydrocarbon as the number of carbon and hydrogen atoms increase?
It increases, as the strength of the intermolecular forces increase, so more energy is required to break them
What is a homologous series?
A series of compounds which have similar chemical properties, but show a gradual variation in physical properties (eg. boiling points)
Name a chemical property of an alkane
They undergo complete combustion and when they burn (react with oxygen) they form carbon dioxide and water
What happens during complete combustion of a hydrocarbon fuel?
Hydrogen is oxidised to H2O
Carbon is oxidised to CO2
Energy is given out
When does incomplete combustion occur?
What happens?
It occurs when there’s a limited supply of oxygen.
Hydrogen is still oxidised to H2O, but carbon may be partially oxidised to form carbon monoxide (CO), carbon may be released as spot and less energy is given out
How is sulfur dioxide formed?
What happens when it dissolves in water in the air?
Hydrocarbon fuels may contain impurities such a sulfur compounds. When these fuels are burnt, the sulfur is oxidised to form sulfur dioxide.
It makes acid rain
State two environmental problems of acid rain
Trees are damaged, enters rivers and lakes which harms organisms
Name a fossil fuel obtained from crude oil and a fossil fuel obtained from natural gas
Crude oil: petrol
Natural gas: methane (domestic cooking and heating)
How is hydrogen manufactured?
The electrolysis of water or the cracking of oil fractions
Name a benefit of hydrogen and a benefit of petrol
Hydrogen: doesn’t produce ash or smoke, only produces water when it burns (petrol makes CO2 and CO)
Petrol: liquid - easy to store and transport (hydrogen is a gas, gas to be stored at high pressures)
What does cracking do?
Breaks down larger alkanes into smaller, more useful alkanes (used as fuels) and alkenes (used to make polymers) by heating
Why is carbon monoxide toxic?
It attaches to the haemoglobin in red blood cells instead of oxygen, reducing the amount of oxygen in the bloodstream
