Chapter 11: Stoichiometry Flashcards
what is stored chemical energy called
enthalpy
define fuel
a substance that can release it’s stored chemical energy easily for heat or power
convert kilo, tera, giga and mega joules into joules
kilojoules: 10^3 J
megajoules: 10^6 J
gigajoules: 10^9 J
terajoules: 10^12 J
what is a non-renewable resource
a resource that is used faster than it is replaced e.g fossil fuels
what is sustainability
finding a middle ground between the short term and long term needs of society
what is the relationship between water and carbon proportion in coal
as the proportion of coal rises the proportion of water decreases
explain what fracking is
fracking is used to extract natural gas
fracking is when a reinforced well is drilled into an coal deposit to create cracks in the coal
fracking fluid (made of water sand and chemicals) at extremely high pressures is pumped
this creates cracks and fissures in the coal and the natural gas can be extracted
this process is done because under high pressures natural gas becomes adsorbed onto the surface of the coal and can’t escape
what is bioethanol
bioethanol is created by fermentation of maize or corn when small sugar molecules are converted to ethanol by enzymes released by yeasts
what is biogas
it is made by anaerobic bacteria that decomposes organic wastes
the breakdown of these organic wastes releases methane and carbon dioxide that can be extracted
used for heating
what is biodiesel
it is created in reaction of vegetable oils or animal fats and a small alcohol molecule such as methanol
it can be 100% used for heavy machinery such as trucks
what is combustion
when a fuel is burnt in the presence of oxygen, releasing heat (exothermic)
2 reasons why excess CO2 is bad
when it dissolves into water it can for H2CO2 (carbonic acid) which causes acidification of the water
this can lead to acid rain
atmospheric CO2 can absorb and reemit heat (greenhouse effect) which results in the trapping of heat, leading to climate change
3 cons of climate change
rising sea levels
climatic changes: increased summer rainfall and decreased winter rainfall in Australia
loss of habitat
name a negative of biogas, bioethanol and biodiesel
biogas: methane is a more effective greenhouse gas than CO2
bioethanol and biodiesel: requires large amounts of resources such as fertilisers and water that can lead to erosion of soil or land degradation over time
define heat of combustion
the enthalpy change of a specified amount when combusted
why aren’t coals and trees heat of combustion measured in kJ mol-1
they are mixtures that do not have a specific molar mass therefore they are measured in kJ g-1
why is deltaH negative in exothermic reactions
deltaH is change in enthalpy so before the substance is combusted the enthalpy is high and then after it is low
therefore it has lost enthalpy and is negative
name 3 factors that go into choosing a fuel
energy released per mass unit or mol
availability of fuel
ease of transportation
hazardousness to people and environment
social, economical and political factors
define energy efficiency
the percentage of energy converted to a useful energy e.g solar panels only convert 17% of energy to useable energy
