Fuels and Hydrocarbons Flashcards
What are crude oil fractions used for?
- In power stations to generate electricity
- In cars, boats, planes as fuels
- To make medicines
- To make plastics and their polymers
Crude oil can be separated using a process called distillation.
Fractional distillation - typical number of hydrocarbons in the chain
Petroleum gas - 3 carbons Petrol - 8 carbons Naphtha - 10 carbons Kerosene - 15 carbons Diesel oil - 20 carbons Fuel oil - 35 carbons Residue (bitumen) - 40 carbons
Complete combustion
When a fuel is burned, hydrogen and carbon both combine with oxygen.
Hydrocarbon + oxygen = carbon dioxide + water
When a fuel is burned in plentiful supply of oxygen complete combustion takes place.
Incomplete combustion
When hydrocarbons burn in a limited supply of oxygen, incomplete combustion occurs.
Carbon monoxide and soot are the additional chemicals produced
Hydrocarbon + oxygen = carbon monoxide + carbon dioxide + water + carbon (soot)
The Alkane family
Methane is first member of alkane family and is the simplest with chemical formula CH4
Alkanes are saturated (no more hydrogens can be added)
Name always ends in -ANE
The combustion of all alkanes:
Alkane + oxygen = water + carbon dioxide
The general formula is:
Cn H2n + 2
What is a homologous series?
A family of compounds which:
Has the same general formula
Similar chemical properties (undergo similar chemical reactions)
The m.p. and b.p., the viscosity of the alkanes, alkanes and cycloalkanes all show an increase going up the series as the number of carbon atoms in their molecules increase.
The cycloalkane family
Cyclopropane is the first member of the family which has molecular formula C3 H6
General formula is:
Cn H2n
Hydrocarbons with bromine solution
Alkane = saturated and no effect on bromine solution
Alkene = unsaturated and decolourises solution
Cycloalkane = saturated and no effect
What are isomers?
Isomers are molecules with the same molecular formula but have different structural formula
Isomers in the Alkane family only occur in molecules with 4 or more carbons
The more carbons in a molecule the more isomers are possible
Uses of alcohols
Alcoholic beverages Deicers Antiseptic - rubbing alcohol Fuels Solvents
Hydroxyl group
The O-H groups of atoms is called the hydroxyl group.
The m.p. and b.p. of the alcohols are higher than their corresponding alkanes because of the hydroxyl group which results in stronger intermolecular forces
General formula is: Cn H(nx2+1) OH
Carbohydrates
Glucose is a member of a group of compounds called carbohydrates
These only contain the elements carbon, hydrogen and oxygen
Glucose is one of the simplest members of this group with molecular formula C6 H12 O6
Glucose - monosaccharide
Fructose - polysaccharide
The ratio of hydrogen : oxygen is always 2:1
Carbon dioxide + water = glucose + oxygen
Alcohols
The m.p. and b.p. of alcohols increase as the number of carbons increase.
The longer the carbon chain, the stronger the intermolecular forces. This means we need more energy to separate the molecules.
Alcohols are soluble in water. Higher alcohols are less soluble.
The pH will be neutral
Alcohols burn with a blue flame
Glucose and starch
Plants convert glucose into starch through a condensation reaction
Glucose is stored in plants as starch
Starch is insoluble
The stored starch is turned back into glucose later and used as energy (respiration)
Glucose to starch = condensation reaction
Starch to glucose = hydrolysis reaction
Making alcohols
Alcohol is made from the fermentation of carbohydrates
Fermentation involves reacting a fruit or vegetable with a fungus known as yeast
Alcohol - source - type of carbohydrate Beer - barley - starch Wine - grapes - sugar Whiskey - barley - starch Vodka - potatoes - starch Sake - rice - starch Cider - apples - sugar Gin - barley - starch
Water + yeast + glucose = ethanol + carbon dioxide
