Chemistry Questions (1 Viewer)

[nightweaver066]

Re: ethanol as a reneweable resource?

yeah i see that
but girlworldclub addressed the infinite source of renewable ethanol etc... then mentioned greenhouse neutral.
i dont think they relate

HAI SIDDY

girlworld_club said what you said was to do with how bioethanol is greenhouse neutral.

First of all, for a resource to be renewable, it must be sustainable, i.e., rate of production must be greater than or equal to the rate of use.

Currently, ethanol is derived through catalytic cracking of hydrocarbons from petroleum. Petroleum is formed through biological & chemical processes for millions of years, and thus will not regenerate at a rate to sustain our use, and so will eventuate deplete.

However, the production of bioethanol from biomass is sustainable with our uses and is thus renewable. So we can see how biomass can be an alternative source of fuel as petroleum resources deplete.

 

[girlworld_club]

molar heat of combustion

How can you improve the molar heat of combustion experiment in terms of accuracy, validity and reliability (considering the experiment was repeat 3 times already)? (don't forget to refer to experimental design)

List as many reasons as to why the theoretical value is less that calculated?


thanks to anyone, i have a few pointers but not enough.

NEWLY ADDED QUESTION **
How to assess the validity of the results obtained, and how to assess the accuracy. are these two linked? how about reliability (the experiment was repeated 3 times)?

 

[deswa1]

Re: molar heat of combustion

What do you have already so we don't double up?

 

[girlworld_club]

Re: molar heat of combustion

Ok.
-Incomplete combustion (but not explanation as to why it lower experimental value).
-Heat loss to surroundings
-Heat absorbed by aluminum can and thermometer.
-somthing about stirring since coke can was used and it's hard to stir since the hole is so tiny.

and the first one
-maintain a small but significant distance from the bottom of the can to the flame to reduce incomplete combustion.

and that's all.

 

[Siddy123]

Re: ethanol as a reneweable resource?

HAI SIDDY

girlworld_club said what you said was to do with how bioethanol is greenhouse neutral.

First of all, for a resource to be renewable, it must be sustainable, i.e., rate of production must be greater than or equal to the rate of use.

Currently, ethanol is derived through catalytic cracking of hydrocarbons from petroleum. Petroleum is formed through biological & chemical processes for millions of years, and thus will not regenerate at a rate to sustain our use, and so will eventuate deplete.

However, the production of bioethanol from biomass is sustainable with our uses and is thus renewable. So we can see how biomass can be an alternative source of fuel as petroleum resources deplete.

Wattup weaaverrr
How u been brah haha?
Sweet thanks!!

 

[someth1ng]

Re: molar heat of combustion

How can you improve the molar heat of combustion experiment in terms of accuracy, validity and reliability (considering the experiment was repeat 3 times already)? (don't forget to refer to experimental design)

List as many reasons as to why the theoretical value is less that calculated?


thanks to anyone, i have a few pointers but not enough.

- Use a bomb calorimeter which insulates around the sides and top of the can but does not insulate the bottom as that must be contacting the flame. This reduces heat loss from the can to the air and water to the air.
- Use a more thermally conductive can (less heat absorbed and more is transferred to the water) - instead of a normal beaker, using a copper can can promote heat transfer.

- As there is nitrogen in the atmosphere in high concentrations, a flame can produce some nitrogen oxides, resulting in varying molar heat of combustion of the fuel.
- Heat from the water is lost to the atmosphere through its contact with the air.

 

[someth1ng]

Re: ethanol as a reneweable resource?

When ethanol combusts, releases CO2 (which causes the greenhouse effect) --> but this same CO2 is taken in by plants for photosynthesis, so there's no CO2 actually lost to the atmosphere --> greenhouse NEUTRAL.

You really should be calling it carbon neutral.

You should also know the arguments that ethanol is NOT an entirely carbon neutral fuel because energy MUST be input into the process to produce ethanol (transport, heating for fermentation, harvesting etc).

 

[girlworld_club]

Re: molar heat of combustion

we used an aluminum can, would using a copper can be an improvement?

 

[nightweaver066]

Re: ethanol as a reneweable resource?

You really should be calling it carbon neutral.

You should also know the arguments that ethanol is NOT an entirely carbon neutral fuel because energy MUST be input into the process to produce ethanol (transport, heating for fermentation, harvesting etc).

Yep. I usually say "carbon neutral" in inverted commas because, as you mentioned, it isn't entirely carbon neutral

 

[golgo13]

Re: ethanol as a reneweable resource?

I would also like to stress that you would require reasons why it isn't used completely right now , questions you should ask yourself, why do we continue to use fossil fuels if we have such a "renewable source" avaliable

 

[Siddy123]

Re: ethanol as a reneweable resource?

I would also like to stress that you would require reasons why it isn't used completely right now , questions you should ask yourself, why do we continue to use fossil fuels if we have such a "renewable source" avaliable

production of ethanol via natural means requires alot of fertile,agricultural land( deforestation of land--> destroying environment etc..) to produce cellulose( growing corn etc..)
new infrastructure such as ethanol fermentation plants must be built, which is very costly and time consuming.
fossil fuels are also cheaper to produce than biomass fuels.
energy via natural means requires high energy and work.

 

[someth1ng]

Re: ethanol as a reneweable resource?

production of ethanol via natural means requires alot of fertile,agricultural land( deforestation of land--> destroying environment etc..) to produce cellulose( growing corn etc..)
new infrastructure such as ethanol fermentation plants must be built, which is very costly and time consuming.
fossil fuels are also cheaper to produce than biomass fuels.
energy via natural means requires high energy and work.

Elaborating on the new infrastructure point, something into more depth is that ethanol has different burn characteristics to other fuels such as octane and so, it cannot be used in the same way and thus, totally new equipment such as engines will be needed.

Also mention that it is a relatively slow process to produce ethanol.

 

[someth1ng]

Re: molar heat of combustion

we used an aluminum can, would using a copper can be an improvement?

Yes, copper is a better thermal conductor - one that is even better than copper is silver but that is not available in schools due to its cost for only a slight improvement.

 

[Siddy123]

Re: ethanol as a reneweable resource?

Elaborating on the new infrastructure point, something into more depth is that ethanol has different burn characteristics to other fuels such as octane and so, it cannot be used in the same way and thus, totally new equipment such as engines will be needed.

Also mention that it is a relatively slow process to produce ethanol.

yeah and shit bout the spark plugs and stuff within the motor need to be changed.
coz the ignition point and flash point etc....
ethanol would explode using standard( petrol) engines

 

[theind1996]

Re: ethanol as a reneweable resource?

yeah and shit bout the spark plugs and stuff within the motor need to be changed.
coz the ignition point and flash point etc....
ethanol would explode using standard( petrol) engines

Lol'd.

Ethanol CORRODES the engines due to its polarity/presence of OH hydroxyl group. So heavy destruction of engines would occur.

Another sub-point you may want to add is a real life example --> Brazil can only produce this much ethanol since it has large amounts of arable land, smaller countries with less arable land will not be able to obtain ethanol through biomass since there's not enough arable land --> need to import ethanol --> more cost and less economically viable.

Another point is that ethanol has less yield compared to petrol --> larger amounts of biomass required since ethanol offers less energy compared to how much is invested in production.

Some of the points I've said are not exactly strictly syllabus, but I guess it doesn't harm anyone if you can expand on the points in exam and write more.

 

[Siddy123]

Re: ethanol as a reneweable resource?

Lol'd.

Ethanol CORRODES the engines due to its polarity/presence of OH hydroxyl group. So heavy destruction of engines would occur.

Another sub-point you may want to add is a real life example --> Brazil can only produce this much ethanol since it has large amounts of arable land, smaller countries with less arable land will not be able to obtain ethanol through biomass since there's not enough arable land --> need to import ethanol --> more cost and less economically viable.

Another point is that ethanol has less yield compared to petrol --> larger amounts of biomass required since ethanol offers less energy compared to how much is invested in production.

Some of the points I've said are not exactly strictly syllabus, but I guess it doesn't harm anyone if you can expand on the points in exam and write more.

hmm yeah good points
but lol what? im srs
with a standard machine engine, the spark plugs( ignite the fuel) send a very strong current, igniting the fuel.
however the flash point of ethanol is much lower, meaning it requires much less energy inorder to ignite.
using existing machinery would result in an explosion.
but yeahhh
pree good thread in terms of new ideas and syllabus not related shit

 

[girlworld_club]

Re: molar heat of combustion

How would you do question five (all of it) in this paper including the graph question - don't need to grow the graph just let me know if you do a line of best fit and connect to the origin.

http://www.boredofstudies.org/cours...951_2002_Chemistry_Assessment_Task_Psyche.pdf

 

[Maddie199589]

Re: ethanol as a reneweable resource?

Ethanol is renewable because we can grow cane sugar which we can make ethanol from

 

[golgo13]

Re: ethanol as a reneweable resource?

I think points missed with why it isn't used is the difference in molar heat of combustion, it takes more moles of ethanol to burn to the equivalent of 1 mole of octance, and another one i remember unless it's changed is that it takes more energy to produce ethanol than it yeilds hence you would be running in a deficit

 

[girlworld_club]

Urgent, heat of combustion question!

In regards to the heat of combustion question:


Suggest how the reliability of your results could be improved (if experiment was repeated 3 times but you had one anomaly out of the three trials)?

Suggest how the accuracy of your results could be improved?

*Using school laboratory equipment, someone suggested a bomb calorimeter but this i not available in high schools.