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FSN Chemistry Unit 4 Exam - Answers (By Collin)
Ahmad:
I have read the question a few times (found the wording a bit tricky) but came to the same conclusion as Collin. I also agree with all his answers posted above.
ninwa:
Yeah, I agree with coblin, and so does my chem teacher.
"The amount of energy in each of these forms that take part in the generation of a fixed quantity of electricity"
By "take part" I'm assuming they mean being involved in the energy conversions which eventually end up as electrical energy. Almost all of the energy obtained from burning the coal would be converted to thermal energy in steam. A greater amount of this thermal energy is converted to mechanical energy, than the amount of mechanical energy converted to electrical energy.
If that makes sense.
If only I saw it this clearly in the exam :( it seems so simple now that I'm not under stress and pressure
Khangfu:
Amount of energy in coal----> many transformation---> electricity. Least amount fo energy from coal
Amount of energy from steam---> mechanical ---> electrical not alot fo energy from steam to electrical
Mechanical --> electrical.
The question asked for the amount of energy in each form converted to electrical. Not how much energy was in the coal initially, in each form... so the chemical energy, a lot of it will be lost and yeah. Really annoying. I know what your saying, that coal has most energy, however most of this energy is lost as waste heat. Not all is converted to electricity. They key is to identify how much of each energy was converted to electricity so basically efficiency.
AkirA:
Question 20 is wrong - it's C, not D. I interpreted it a different way.
Collin Li:
--- Quote from: "Khangfu" ---Amount of energy in coal----> many transformation---> electricity. Least amount fo energy from coal
Amount of energy from steam---> mechanical ---> electrical not alot fo energy from steam to electrical
Mechanical --> electrical.
The question asked for the amount of energy in each form converted to electrical. Not how much energy was in the coal initially, in each form... so the chemical energy, a lot of it will be lost and yeah. Really annoying. I know what your saying, that coal has most energy, however most of this energy is lost as waste heat. Not all is converted to electricity. They key is to identify how much of each energy was converted to electricity so basically efficiency.
--- End quote ---
There's no way your interpretation makes sense, since the question says:
"The amount of energy in each of these forms that take part in the generation of a fixed quantity of electricity is, from lowest to highest."
For a fixed quantity of electricity, the amount of energy is 100% from the coal, steam and the turbine, it's just that the coal, steam and turbine also produced other forms of energy.
We actually need to find out, for a fixed quantity of electricity, how much input do we need of each form of energy so that we will get that same fixed quantity of electricity. This then answers the question: which forms of energy require the most "energy input" in order to yield the fixed quantity of electricity we are supposed to produce.
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