Someone PLEASE help with this Prac (1 Viewer)

[keepin_sanity]

i really really really need you guys to help me out here!!!


I have been through my notes about a million times and I'm absolutely positive that we didn't do a prac corresponding to this dotpoint:

identify data sources, choose resources and perform a first-hand investigation to determine and compare heats of combustion of at least three liquid alkanols per gram and per mole


If anyone could post or PM the method results, etc to me I would forever be in your debt...knowing my luck there will be a question on it in the HSC!

Thanks in advance!!!

 

[chip]

please post it if anyone has it cause i didnt do nay pracs all year and am in need of help also

 

[jm1234567890]

Ingredients:
- butanol
- pentanol
- hexanol
in lamp form
- calirometer (can)
- retort stand with clamp
- temperature probe

Setup:
you know what it looks like

Method:

- measure 100ml of water
- put water in calorimiter
- measure initial temperature of water
- measure weight of lamp
- light lamp under calorimiter
- heat until noticiable temperature change (ie a few degrees)
- weight lamp again
- record
- change in weight of lamp
- change in temperature
- amount of water used
- repeat 3 times
- repeat for other lamps

use the heat of water equation to figure out molar heat of combustion, you know what i mean.

and thats it.

 

[keepin_sanity]

Thankyou thankyou thankyou!!!

I really appreciate that...now I'm destined to pass the HSC

 

[toknblackguy]

hahahahaha
just remember that to improve reliability (?) u gotta have wick as close as possible to the thing, juse a conical flask cause it's got a larger base and uses more of flame, ummm...u can say errors include heat lost to surrounding and to flask
cheers

 

[parry]

we just used a cut open aluminum can to hold the water

 

[Frigid]

improving validity:

• in your procedure say you used beaker; to improve say you will change and use copper/aluminium - what's wrong with that? cheap-cheap free mark
• say you used electronic balance with more decimal places - from 2 dp to 3dp (even tho the 3dp's cost like $1K each).
• say you got removed all the draughts in the room by shielding and closing windows.
• say you made aluminium foil shielding which reflected the heat back into the apparatus.

 

[toknblackguy]

how does using cu/al imrpove it over a beaker?
wouldn't that conduct more heat, meaning more heat lost to surroudnings as opposed to more heat conducted through to water?

 

[ND]

Glass has a higher specific heat capacity, so more energy goes into heating it up.

 

[Frigid]

bro, you gotta realise glass is a bad conductor of heat. it's specific heat value is like ten times greater than copper (whose value is like 0.38 J/K/mol, i think, off the top of head)...

so what does this mean in the real world?

okay, we have glass beaker, it sucks heat from the flame, transfers that heat energy to the water. but because it's not a very good conductor, it will require more energy from the spirit burner to heat the water for a specific delta-T. therefore we lose accuracy because glass is such a 'heat-hog' (excuse the term)...

copper, on the other hand, because it's a very good conductor of heat (and electricity i might add), does not keep the heat; instead, it transfers almost all of it to heating the water.

since we are trying to determine the molar heat of combustion based on how much fuel we need to cook some water the more energy we apply to heating the water (and not the container) the better.

an interesting sidenote, copper and aluminium, because of their good conductive properties, are used as the humble heatsinks on your very CPU.

 

[ND]

Originally posted by Frigid
bro, you gotta realise glass is a bad conductor of heat. it's specific heat value is like ten times greater than copper (whose value is like 0.38 J/K/mol, i think, off the top of head)...

so what does this mean in the real world?

okay, we have glass beaker, it sucks heat from the flame, transfers that heat energy to the water. but because it's not a very good conductor, it will require more energy from the spirit burner to heat the water for a specific delta-T. therefore we lose accuracy because glass is such a 'heat-hog' (excuse the term)...

copper, on the other hand, because it's a very good conductor of heat (and electricity i might add), does not keep the heat; instead, it transfer almost all of it to heating the water.

since we are trying to determine the molar heat of combustion based on how much fuel we need to cook some water to more energy we apply to heating the water (and not the container) the better.

an interesting sidenote, copper and aluminium, because of their good conductive properties, are used as the humble heatsinks on your very CPU.

You and your long responses...

 

[mon_mon]

Man, i hope you write quickly. otherwise oyurgonna run out of time very quickly.

 

[inasero]

cook some water

hmmm...an interesting proposal

 

[mon_mon]

sound like home ec.

 

[pganglia]

i really really really need you guys to help me out here!!!


I have been through my notes about a million times and I'm absolutely positive that we didn't do a prac corresponding to this dotpoint:

identify data sources, choose resources and perform a first-hand investigation to determine and compare heats of combustion of at least three liquid alkanols per gram and per mole


If anyone could post or PM the method results, etc to me I would forever be in your debt...knowing my luck there will be a question on it in the HSC!

Thanks in advance!!!

thank u for asking this question, I have exactly the same question in my assessment (word by word) thanks heaps.
and to the great answer provided.