Fuels Flashcards
What is combustion
Fuels that store chemical energy, can be harnessed
Release of energy in presence of oxygen = Combustion
What is combustion as a chemical process
Is an exothermic reaction, oxygen as reactant, oxide as product
No atoms created/destroyed
Balanced equation tells you n(Molecules) of Oxygen required for each molecule of propane
What is complete combustion of hydrocarbons
Oxygen supply sufficient
Carbon Dioxide & Water produced
What is incomplete combustion of hydrocarbons
Oxygen supply limited
Carbon Monoxide & Water produced
How do you write equations for combustion reactions
Reactants: Oxygen and hydrocarbon
Products: Either water & carbon dioxide (Complete combustion) or water & carbon monoxide (Incomplete combustion)
Balance equation
Add state symbols
What is carbon dioxide
Complete combustion of carbon-based fuels
Significant greenhouse gas (Global warming)
What is carbon monoxide
Incomplete combustion of carbon-based fuels
Toxic gas
What is sulfur dioxide
By-product of combustion of sulfur-containing fuels
Toxic gas
What is methane
Decomposition of organic matter in absence of oxygen
Greenhouse gas
What is oil
Fossil fuel
Hazardous to environment if spilt
What does the amount of carbon in fuel influence
Amount of carbon in fuel influences:
- Amount of energy released during combustion
- Amount of oxygen for complete combustion
- Amount of carbon dioxide released
How to calculate amount of carbon in fuel
If amount of carbon is % of total fuel
m(Carbon = (%/100) * m(Fuel)
To determine percentage of carbon content
- Find percentage composition
- Higher % carbon, higher energy content of fuel
What are mass to mass calculations
Possible to determine mass of one chemical in chemical reaction when mass of other chemical known
What are the steps of mass to mass calculations
Write a balanced chemical equation
Calculate molar mass of chemicals
Determine molar ratio of required substances
Rearrange equation to find using ratios
What is the energy content of fuels
All substances have chemical energy = Energy content
- Fuels have high energy contentWh
What is heat of combustion
Enthalpy change when specified amount (1 mol) of fuel completely burns in oxygen (kJ / mol)
- Amount of energy released by mass of fuel is based on n(Moles of fuel)
- Energy = n(Moles) * Heat of Combustion
What are the steps to determine energy released
Determine chemical formula & molar mass of fuels
Calculate n(Moles) in given mass
Use formula to calculate energy released, or rearrange for something else
What is a fuel
Substance with stored energy, can be released easily as heat/power
What are fossil fuels
Non-Renewable
From ancient plants, animals, microorganisms
What are biofuels (Biochemical Fuels)
Renewable
From plant material / animal fats
- Create competition for land that might be used for food
Not added to net Carbon Dioxide in atmospher
What is the type of fossil fuels
Coal
Oil
Petrol
Natural Gas
What is the type of biofuels
Bioethanol
Biogas
Biodiesel
What is coal
Mixture of large molecules made from carbon, hydrogen, nitrogen, sulfur
High carbon emissions
What is natural gas
Found in deposits in Earth’s crust
Popular for home heating & cooking
What is petroleum / crude oil
Mixture of hydrocarbon molecules, mostly alkanes
No use itself as fuel, components can be made into important fuels
What is bioethanol
Fermentation of sugars to ethanol
Is ethanol produced differently
What is biogas
Breakdown of organic waste by anaerobic (Limited oxygen) bacteria
What is biodiesel
Mixture of organic compounds produced by chemical reactions between oils / fats & alcohol
When comparing fuels, what are fossil fuels
Generally higher energy content
Higher level of carbon emissions
When comparing fuels, what are biofuels
Lower energy content
No / Very little carbon emissions
