Chemistry Questions (1 Viewer)

someth1ng · Nov 25, 2012

Re: Does anyone have detailed notes on these two experiments.

Based on your method, your experiment was NOT reliable because you didn't state that it was repeated and you didn't mention consistency of results.

For accuracy, you might want to compare the masses originally to determine how much CO2 was lost.

"keeping constant temperature maximises the overall yield" is nit necessarily correct - only when at ~37C. This line implied that it was true at any temperature.

For the test of ethanol, I can never understand why you use drops of Br2 on C2H4 because it is a gas, not a liquid. I prefer something like the dehydration of ethanol produces a gas and if this gas is captured and bubbled through bromine water, the bromine water should decolourise.

study-freak · Nov 25, 2012

Re: Does anyone have detailed notes on these two experiments.

someth1ng said:
Based on your method, your experiment was NOT reliable because you didn't state that it was repeated and you didn't mention consistency of results.

For accuracy, you might want to compare the masses originally to determine how much CO2 was lost.

"keeping constant temperature maximises the overall yield" is nit necessarily correct - only when at ~37C. This line implied that it was true at any temperature.

For the test of ethanol, I can never understand why you use drops of Br2 on C2H4 because it is a gas, not a liquid. I prefer something like the dehydration of ethanol produces a gas and if this gas is captured and bubbled through bromine water, the bromine water should decolourise.

Nah.
It's just that reliability can't be assessed - doesn't mean it wasn't.

someth1ng · Nov 25, 2012

Re: Does anyone have detailed notes on these two experiments.

study-freak said:
Nah.
It's just that reliability can't be assessed - doesn't mean it wasn't.

The dotpoint is "monitor mass changes" which CAN be assessed. Therefore, you need to repeat the experiment and look at the consistency of results (similar mass changes).

ie. Are the mass changes similar if you repeat the experiment (each test)?

someth1ng · Nov 25, 2012

Re: Does anyone have detailed notes on these two experiments.

study-freak said:
Nah.
It's just that reliability can't be assessed - doesn't mean it wasn't.

The dotpoint is "monitor mass changes" which CAN be assessed. Therefore, you need to repeat the experiment and look at the consistency of results (similar mass changes).

ie. Are the mass changes similar if you repeat the experiment (each test)?

study-freak · Nov 25, 2012

Re: Does anyone have detailed notes on these two experiments.

someth1ng said:
Based on your method, your experiment was NOT reliable because you didn't state that it was repeated and you didn't mention consistency of results.

For accuracy, you might want to compare the masses originally to determine how much CO2 was lost.

"keeping constant temperature maximises the overall yield" is nit necessarily correct - only when at ~37C. This line implied that it was true at any temperature.

For the test of ethanol, I can never understand why you use drops of Br2 on C2H4 because it is a gas, not a liquid. I prefer something like the dehydration of ethanol produces a gas and if this gas is captured and bubbled through bromine water, the bromine water should decolourise.

someth1ng said:
The dotpoint is "monitor mass changes" which CAN be assessed. Therefore, you need to repeat the experiment and look at the consistency of results (similar mass changes).

ie. Are the mass changes similar if you repeat the experiment (each test)?

Of course you can assess reliability if you repeat the experiment, but his method does not specify this and on this basis, you claimed that his results are unreliable. I'm saying this is incorrect because it simply doesn't make sense to talk about (un)reliability of results without any repetition.

(N.B. I don't like saying 'unreliable experiment' as it's really the result(s) you are talking about)

someth1ng · Nov 26, 2012

Re: Does anyone have detailed notes on these two experiments.

I see what you mean now but yeah, I guess you're right. I think it's best to say that the reliability is questionable or something like that.

golgo13 · Nov 27, 2012

Re: Does anyone have detailed notes on these two experiments.

I thought that reliability is the ability to follow the procedure word for word basically. Unless it's the reliability of the results for which it's arguable to say that it's questionable but to i guess improve on that is to measure it against widely accepted values?

nerdasdasd · Nov 27, 2012

golgo13 said:
I thought that reliability is the ability to follow the procedure word for word basically. Unless it's the reliability of the results for which it's arguable to say that it's questionable but to i guess improve on that is to measure it against widely accepted values?

Reliability is how close all of of the results are . Validity is the ability to follow the procedure .

girlworld_club · Dec 8, 2012

what's the big deal of ethanol being renewable?

this is put quite bluntly, but it's my question.

Apple Sauce · Dec 8, 2012

Re: ethanol as a reneweable resource?

It allows a renewable source of fuel for the future. At the moment (this day and age) the majority of hydrocarbons are producted from petroleum (i.e. non nenewable). By creating ethanol from renewable sources, such as bacteria or vegetation, it allows for the continued products to be made in the future (i.e. hydrocarbons= plastics)

Siddy123 · Dec 8, 2012

Re: ethanol as a reneweable resource?

ethanol can be derived from the process of fermentation of glucose ( a non-fossil fuel( petroleum) source), meaning that it is renewable and enviro-friendly.
It can also be derived from the decomposition of bacteria within cellulose or from starch. ( completely natural)

Ethanol is considered renewable as when it is combusted it results in Carbon dioxide and molecules of water which can be used to form glucose by the process of photosynthesis---> fermented by yeast--> ethanol

C2H50H+302-->2CO2+ 3H20

Please note that distillation occurs at the end of the process which requires great amounts of heat energy which come from sources of a non-renewable nature.
so we're using non-renewable sources to make renewable sources...

girlworld_club · Dec 8, 2012

Re: ethanol as a reneweable resource?

isn't the main point of it being renewable is that it is an infinite resource, what you said falls under the "greenhouse neutral argument"?

theind1996 · Dec 8, 2012

Re: ethanol as a reneweable resource?

Well ethanol can be produced from glucose which is derived from natural resources.

When plants take in sunlight, they undergo photosynthesis --> glucose is one of the products from photosynthesis --> used for the fermentation process which produces ethanol --> when ethanol combusts, CO2 and H2O are the products --> the CO2 is released into the atmosphere, but the greenhouse effect is negated by the fact that plants take in equal amounts of CO2 and H2O to undergo photosynthesis --> they produce glucose --> repeated cycle of ethanol production.

As a result of all this, ethanol is a renewable fuel as plants can be continuously grown to produce ethanol (since plants won't die out most of the time) and so ethanol can be continuously produced for the future --> hence it is known as a renewable resource.

Siddy123 · Dec 8, 2012