Chemistry marathon (1 Viewer)

[nerdasdasd]

Post questions up and then someone answer it

 

[nerdasdasd]

I'll start, what is the role of refuxing in the production of esters ?

 

[ZombieApocalypse]

to stop volatile substances escaping (which may be a health risk), to increase yield of the ester, and to allow the reactants to be heated



what measures have been taken to reduce the use of cfcs?

 

[nerdasdasd]

to stop volatile substances escaping (which may be a health risk), to increase yield of the ester, and to allow the reactants to be heated



what measures have been taken to reduce the use of cfcs?

The phasing out of the CFCs and the introduction of chemicals with much less depletion potential such as hcfcs and HFCs

 

[ZombieApocalypse]

The phasing out of the CFCs and the introduction of chemicals with much less depletion potential such as hcfcs and HFCs

answer it properly

what lead to the phasing out.

Also, HFCs has an ODP of 0%

 

[unLimitieDx]

Montreal Protocol.
Refluxing also eenables esterification to occur at high temperature

 

[nightweaver066]

.. two of my marathon threads have been replaced LOL

 

[nerdasdasd]

answer it properly

what lead to the phasing out.

Also, HFCs has an ODP of 0%

The discovery of the ozone hole over the Antarctica and the reducing ozone levels ( dobson units).

 

[ellie95]

Explain how structure and properties of polyethylene and polystyrene is related to the way it is used

4 marks

 

[nightweaver066]

Should allocate marks to the questions to give people a general idea of the detail they should give.

 

[nerdasdasd]

Explain how structure and properties of polyethylene and polystyrene is related to the way it is used

4 marks

Do we have to include ldpe and hdpe ?

 

[ellie95]

Do we have to include ldpe and hdpe ?

yeah I would

 

[unLimitieDx]

Polyethylene - low density --> highly branched carbon chains -> weak disp. forces thus soft, flexible --> cling wrap
-high densitry --> unbranched carbon chains enabling molecule to pack tightly and experience stronger dispersion forces ---> more rigid and inflexible, higher mp than LDPE --> plastic crates, rubbish bins
Polystyrene - bulky benzene ring in its structure --> hard and inflexible
-> crystalline polystyrene - hard, brittle - medicine cups
-> styrofoam - lightweight insulator, shock absorbance - insulating cups and eskies

 

[smalik]

LDPE has larger degree of cross linking and a lower degree of branching making it transparent, flexible, low density USES: Transparent food wrapping, sandwhich bags
HDPE: Lower degree of cross linking and higher degree of branching making it non transparent, inflexible, hard, higher density USES: Wheely bins and hard lunch boxes
Blown styrene has low density, large amounts of trapped air making it able to be used as a thermoinsulator for coffee cups and also a shock absorber in packaging
Solid Styrene has a higher density but still low by comparison to other polymers, making it used for surfboards

 

[Sy123]

 

[nerdasdasd]

yeah I would

Ok, hmmmmmmm. The use of polyethylene and polystyrene are highly determined by its properties and structure. Polyethylene can be produced to have an linear or branched form. Ldpe or branched polyethylene has many branches in its molecular structure, and as a result, is highly weak and this makes it useful in product such as shopping and sandwich bags. Hdpe, in comparison had an highly linear structure, resulting in its hardness and rigidness, thus making it useful as materials for products such as pipes for carrying liquids.

 

[Dedication_]

Realising how fucked I am for chem when I see the stuff you guys are asking/answering.

 

[unLimitieDx]

Not sure if this is correct but
i) 3k/11

ii) none? unless i misunderstood the question

 

[smalik]

Explain how a buffer in a natural system maintains a relatively constant pH (Include relevant chemical equations in your answer) ---3

 

[Sy123]

Not sure if this is correct but
i) 3k/11

ii) none? unless i misunderstood the question

First one is correct, second is not. Just assume another chemical equation with k grams of CO as the product and excess O (assume incomplete combustion etc etc) I probably should of made that clear