Chemistry Debates (1 Viewer)

[Dreamerish*~]

This thread is for those assess and evaluate questions where you need two sides of an argument and a judgement.

So let's start arguing about something.

Ethanol does NOT have great potential as an alternative fuel.

I'll go for affirmative.

 

[s_t_a_r1234]

do you actually get asked questions like that for a chemistry paper?

 

[Dreamerish*~]

do you actually get asked questions like that for a chemistry paper?

No, you don't get debates.

You would get questions similar (or identical, if I'm lucky) to:

Assess the potential of ethanol as an alternative fuel.

Evaluate the success of ethanol in replacing petrol as an alternative fuel.

Assess the benefits and problems associated with the use of one radioisotope in medicine.

And so on.

 

[Haku]

i would go against ethanol used as an alternate fuel. i got a 6mark question on that in the half-yearly and i went for ethanol for the environment and renewability and combustion and cleans the engines and all that crap and i got 2 marks.

as for medicine, definitely go for it

 

[Dreamerish*~]

i would go against ethanol used as an alternate fuel. i got a 6mark question on that in the half-yearly and i went for ethanol for the environment and renewability and combustion and cleans the engines and all that crap and i got 2 marks.

as for medicine, definitely go for it

Don't you look at both sides?

Usually it asks you to look at both disadvantages and advantages, and make a judgement. Your judgement doesn't matter a whole lot, as long as you have the ads and disads listed correctly.

 

[Haku]

well thats what i did, but i think i listed more disadvantage than advantage and assessed that it is a viable fuel source

 

[Trebla]

Funny you should ask that, because that is an issue being raised and considered in the public and the government at the moment, with the rocketing prices of petrol. In the news, both sides were presented. I won't be surprised if a question concerning ethanol as an alternative fuel source would appear in the exam, considering the current economic context. I reckon a question like that would be highly likely to appear in the exam or if not, then next year's exam.

 

[The_highwayman]

yeah, our HSC has already been set, long before the recent petrol price increases.

 

[Dreamerish*~]

Funny you should ask that, because that is an issue being raised and considered in the public and the government at the moment, with the rocketing prices of petrol. In the news, both sides were presented. I won't be surprised if a question concerning ethanol as an alternative fuel source would appear in the exam, considering the current economic context. I reckon a question like that would be highly likely to appear in the exam or if not, then next year's exam.

They ask an ethanol question just about every year.

I'm going to list all the disadvantages:

• It is extremely costly to distillate ethanol. It is 100% water-soluble, which means obtaining 100% ethanol is very difficult.
• Up to 11-13% of ethanol can be used in current cars without engine modification.
• Ethanol has a lower heat per gram than petrol, therefore larger tanks are required because one would need a larger volume of ethanol to travel the same distance with petrol.
• While ethanol is a renewable fuel, it is considerably cheaper to obtain ethanol from hydration of ethene than fermentation. Therefore ethanol is only significantly cheaper if our fuel is still manufactured from petrochemicals.
• Large amounts of land need to be cleared in order to grow crops for fermentation. This raises the ethical issue of growing crops for fuel, not food.
• Smelly fermentation wastes present disposal problems, and are a hazard to the environment.
• Although ethanol undergoes complete combustion, large amounts of energy is put into distilling it.

Advantages, anyone?

 

[serge]

Ethanol is good becuase-

It's better than fuels like methane and natural gas
because its a liquid at room temperature (BP at 75 i think?)
which makes it easy to store

It's renewable, since the products of its combustion can be used by plants
in photosynthesis to make sugar which can make more ethanol etc.

It has an oxygen atom attached so incomplete combustion is rare

currently if ethanol is subsidised it can be a successful replacement for octane (like in Brazil)

Since fossil fuels are going to run out we might aswell look for alternatives

anyone remember any other advantages?

 

[Dreamerish*~]

Ethanol is good becuase-

It's better than fuels like methane and natural gas
because its a liquid at room temperature (BP at 75 i think?)
which makes it easy to store

It's renewable, since the products of its combustion can be used by plants
in photosynthesis to make sugar which can make more ethanol etc.

It has an oxygen atom attached so incomplete combustion is rare

currently if ethanol is subsidised it can be a successful replacement for octane (like in Brazil)

Since fossil fuels are going to run out we might aswell look for alternatives

anyone remember any other advantages?

There really aren't that many.

Ethanol is produced from glucose, which was made via photosynthesis from carbon dioxide and water. When ethanol is burned as a fuel, the products are also carbon dioxide and water, which means that ethanol does not produce other pollutants such as carbon and carbon monoxide that are produced by petrol during incomplete combustion.

I think ethanol is a pretty crappy fuel, but it's the best alternative we have.

 

[serge]

you're right
it's not that great a fuel

the enthalpy is low
and even though it's renewable, Carbon Dioxide and Water
are still Greenhouse gases so even though it seems
enviromentally friendly at first in the long term it wont
be that much better than octane

 

[Haku]

Ethanol is good becuase-

It's better than fuels like methane and natural gas
because its a liquid at room temperature (BP at 75 i think?)
which makes it easy to store

It's renewable, since the products of its combustion can be used by plants
in photosynthesis to make sugar which can make more ethanol etc.

It has an oxygen atom attached so incomplete combustion is rare

currently if ethanol is subsidised it can be a successful replacement for octane (like in Brazil)

Since fossil fuels are going to run out we might aswell look for alternatives

anyone remember any other advantages?

another really cool advantage is that because ethanol is a solvent of both polar and non-polar substance is can clean out the gummy and oily bits in the engine. It also combust more fully providing a greater octane rating than petrol, but enthalpy isn;t as high. Also it reduces green house gas emission by 35-40 percent.

i dun really get how it reduce green house gas as it produce CO2 as well, but just no CO cause of more full combustion. So more ethanol needs to be burnt cause of the lower enthalpy so which in turn would more or less produce same amount of green house gas which is CO2. Someone explain


Another totaly unrelated question. How does CO2 react with calcium carbonate (limewater). thats for doing the fermentation experiment. How is CO2 visible in the test tube of calcium carbonate. Please provide an equation.

 

[azza_3761]

i dun really get how it reduce green house gas as it produce CO2 as well, but just no CO cause of more full combustion. So more ethanol needs to be burnt cause of the lower enthalpy so which in turn would more or less produce same amount of green house gas which is CO2. Someone explain

Ethanol doesn't actually reduce the amount of greenhouse gases it just doesn't create anymore (assuming that distillation of ethanol and the cultivation of the glucose don't create any extra CO2). Using ethanol would only reduce the amount of greenhouse gases produced when comparing it to octane or other fuels.

Another totaly unrelated question. How does CO2 react with calcium carbonate (limewater). thats for doing the fermentation experiment. How is CO2 visible in the test tube of calcium carbonate. Please provide an equation.

The limewater turns a milky white colour when CO2 is passed trough it. Don't know the equation

 

[Dreamerish*~]

Another totaly unrelated question. How does CO2 react with calcium carbonate (limewater). thats for doing the fermentation experiment. How is CO2 visible in the test tube of calcium carbonate. Please provide an equation.

You know why it makes no sense? Because limewater is calcium hydroxide.

Calcium carbonate is found in limestone. It is a white precipitate.

When carbon dioxide is present in the clear Ca(OH)₂ solution, it reacts with the calcium hydroxide:

Ca(OH)_2(aq) + CO_2(g) → CaCO_3(s) + H₂O_(l)

The precipitate CaCO₃ suspends in the solution, making it opaque or milky.

 

[Haku]

haha, thanks for clearing that up, ive being calling lime water calcium carbonate all these years and no one corrected me!! lol.

just last night i was thinking of the equation for CO2 and limewater that make the lime water murky...can't get it.

CaCO3 + CO2 ---> ?????

 

[The_highwayman]

you're right
it's not that great a fuel

the enthalpy is low
and even though it's renewable, Carbon Dioxide and Water
are still Greenhouse gases so even though it seems
enviromentally friendly at first in the long term it wont
be that much better than octane

But it means that the demand on regular petrochemicals is lowered...thats another advantage. Really, when u think about it, we really dont need crude oil for anything, we can make biopolymers for plastics and use other forms of fuel...only coz its relatively cheap...

 

[Dreamerish*~]

Yeah, crude oil is mainly used for fuels.

My theory is, the invention of everything that eats up resources is going to bite us in the ass one day.

Who's up for discussing CFCs next?

 

[Haku]

*raises hand enthusiastically*

boys and girls, remember when answering current developments on CFC menting things like HCFC, HFC, and other thing which have a alot lower ODP.

but remember to mention one important thing ... The Montreal Protocol, i think that is the most important to conserving and phasing out the use of CFC and HCFC.

 

[Dreamerish*~]

I'll provide the questions.

What are CFCs and how do they destroy ozone?