10.-Energy-Content-of-Fuels Flashcards
What is a fuel?
Most fuels are organic compounds containing carbon, hydrogen, and sometimes oxygen.
What happens when a fuel is ignited?
It undergoes combustion.
How do we obtain fuels from crude oil?
Crude oil is a mixture of substances made up mainly of hydrocarbons.
What are the main hydrocarbons in crude oil?
Most of the hydrocarbons in crude oil are alkanes.
What is fractional distillation?
Crude oil is separated into many useful fractions by the process of fractional distillation.
What is the process of fractional distillation?
Heat crude oil into a vapour in a furnace, then pass vapour through a fractionating column.
What happens as the length of the carbon chain increases?
Darker in colour, more viscous, less flammable, and sootiness of flame increases.
What are alcohols in the context of fuels?
Alcohols are another homologous series of organic compounds.
What is the general formula for alcohols?
C𝑛 H2𝑛+1 OH
What are the first five alcohols?
Methanol, Ethanol, Propan-1-ol, Butan-1-ol, Pentan-1-ol.
How can methanol and ethanol be obtained?
They can be obtained from renewable energy sources.
What is the chemical equation for ethanol combustion?
ethanol + oxygen → carbon dioxide + water
C2 H5 OH + 3O2 → 2CO2 + 3H2 O
Why is the use of ethanol considered carbon neutral?
The CO2 produced is used for photosynthesis by the plants grown to produce the ethanol.
What are the hazards associated with fuels?
Toxicity, flammability, and risk of explosion.
What is an example of a toxic fuel?
Methanol can attack the central nervous system and may lead to blindness, coma, or death.
What occurs during incomplete combustion?
Carbon monoxide gas and carbon can form, as well as carbon dioxide.
What is carbon monoxide?
A toxic, colourless, and odourless gas that can lead to asphyxiation.
What are particulates?
Soot formed when burning hydrocarbons that can cause respiratory problems.
What is the effect of sulphur impurities in fossil fuels?
They react with oxygen to form sulphur dioxide, which can cause respiratory problems.
What is the consequence of sulphur dioxide in the atmosphere?
It can produce sulfuric acid, leading to acid rain.
What are the different units of energy?
Joules (J), kilojoules (kJ), calories (cal), kilocalories (kcal), and kilowatt-hours (kWh).
What is the equation to find heat energy released by a fuel?
Heat energy = Mass of water × Specific heat capacity of water × Temperature rise of water.
What is a bomb calorimeter?
An apparatus designed to reduce heat loss and ensure complete combustion.
What happens when a fuel is burnt?
Energy is needed to break bonds in the reactants and released when new bonds form in the products.
What is the heat energy released by the first five alcohols?
Methanol: 726 kJ mol-1, Ethanol: 1367 kJ mol-1, Propan-1-ol: 2017 kJ mol-1, Butan-1-ol: 2675 kJ mol-1, Pentan-1-ol: 3323 kJ mol-1.
