Question Chain Thread !!! (1 Viewer)

[JasonNg1025]

A solution is clear in phenolphtathlein and blue in bromothymol blue. In what pH range does the solution lie?

Hey, Jason, how rich would you be if you had a dollar for every time someone asked you that? =P

Very?

7.6 < pH < 8.3

 

[eddy11]

is oxygen probe a good enough test as apposed to winklers method

 

[hoochiscrazy]

Difference between quantitative and qualitative?

 

[squeenie]

Difference between quantitative and qualitative?

Quantitative: Relating to amount of substance
Qualitative: Relating to chemical/physical properties

HSC 05:

Assess the impact of the recent development of a named biopolymer on society and the environment.

 

[Azreil]

Deduce why different metals produce different colours during flame tests

I'm probably way over complicating this in my head, because I'm going into stuff I did in the uni course

Because all elements have different electron shells; the amount of energy released and absorbed is related to the electron subshell arrangement. The energy released/absorbed is therefore related to the colour that is produced on the spectra of light.

Yeah, sorry if that makes no sense.

Describe the layered structure of the atmosphere, making reference to altitude, pressure and temperature.

 

[JasonNg1025]

Describe the layered structure of the atmosphere, making reference to altitude, pressure and temperature.

The atmosphere is made up of 3 main layers - the troposphere, the stratosphere and the ionosphere. The ionosphere is divided into the mesosphere and thermosphere.

The troposphere is the area of altitude 0 to 15km from the surface of the Earth. It has variable temperature as this is where weather is determined. From what I remember, pressure is around 100kPa...

The stratosphere is the area from 15 to 50km above the Earth surface. It contains ozone and other gases and its temperature ranges from -50^o C to 30^o C

The ionosphere ranges from 50km to around 150km above the Earth's surface. There is no solid end to the atmosphere. This area contains ions and atomic particles and has a temperature of around -50^o C

 

[:::a:::]

QUESTION on indicators:


do we need to know the ranges of all indicators (or at least the main ones e.g. bromothyl blue, methyl orange, phenolphthalein and litmus) ?


if so which ones? my textbook only shows as above.

 

[danz90]

is oxygen probe a good enough test as apposed to winklers method

Yep, you just need to know one method to test for oxygen quantitatively.

I've learnt the Oxygen Sensor - basically its an electrolytic cell where oxygen is reduced/oxidised??. The rate of electrolysis/reduction is proportional to the concentration of oxygen.
Gotta go over this one again...

----

For the question about flame tests.

Different elements have different atomic radii.
When you place gaseous cations in a flame, electrons move up an energy level (to a higher electron shell), then move back down to their original state. The energy absorbed when moving up, is released when moving back down. The 'distance' of the energy travelled to the lower energy level determines the wavelength of the light emitted. Since different wavelengths (because of differing atomic radii) produce light of different colours, different metallic cations will produce different coloured flames.

 

[danz90]

QUESTION on indicators:


do we need to know the ranges of all indicators (or at least the main ones e.g. bromothyl blue, methyl orange, phenolphthalein and litmus) ?


if so which ones? my textbook only shows as above.

I think the ones you have to memorise are:

Phenolphthalein (8.3-10.0)
Methyl Red (3.2-4.4)
Methyl Orange (??)
Bromothymol Blue (5.0-7.6)

 

[Azreil]

Assess the impact of the recent development of a named biopolymer on society and the environment.

The development of Poly(3-hydroxybutanoate) has occured in recent times. It has several qualities and hence a wide range of uses: fireproof, able to hold dye, hard wearing and soft to touch -- the large quality of it, however, is that it is biodegradable and renewable.

Considerable research has gone into the possiblity of genetically engineering the bacteria alcalignes eutrophus to produce larger quantities of PHB. Currently, however, the quantity of PHB produced when the bacteria is harvested and dried varies between 30-80%. It is therefore much more expensive to produce than it's synthetic counterparts.

While PHB has had minimal impact on society at the current time, biodgrability and renewability are becoming increasingly important. PHB could have a large and positive effect on the environment by replacing non-renewable resources and reducing landfill. To society, it may increase the cost of polymers however it is already recieving demand in industries where biodegradability is a large concern such as medicine.

Outline a method of determining the presence of heavy metals in a sample.

 

[Pwnage101]

For the question about flame tests.

Different elements have different atomic radii.
When you place gaseous cations in a flame, electrons move up an energy level (to a higher electron shell), then move back down to their original state. The energy absorbed when moving up, is released when moving back down. The 'distance' of the energy travelled to the lower energy level determines the wavelength of the light emitted. Since different wavelengths (because of differing atomic radii) produce light of different colours, different metallic cations will produce different coloured flames.

PS (for u non Physicists), the light released is quantised, hence the 'line' spectra, and not continuous spectrum

i wont even go into how electrons exhibit wave-particle duality, or go into Pauli's exclusion principle or hesienberg's uncertainty principle

...lol, good stuff...quantum physics...i miss it already

 

[danz90]

Assess the impact of the recent development of a named biopolymer on society and the environment.

The development of Poly(3-hydroxybutanoate) has occured in recent times. It has several qualities and hence a wide range of uses: fireproof, able to hold dye, hard wearing and soft to touch -- the large quality of it, however, is that it is biodegradable and renewable.

Considerable research has gone into the possiblity of genetically engineering the bacteria alcalignes eutrophus to produce larger quantities of PHB. Currently, however, the quantity of PHB produced when the bacteria is harvested and dried varies between 30-80%. It is therefore much more expensive to produce than it's synthetic counterparts.

While PHB has had minimal impact on society at the current time, biodgrability and renewability are becoming increasingly important. PHB could have a large and positive effect on the environment by replacing non-renewable resources and reducing landfill. To society, it may increase the cost of polymers however it is already recieving demand in industries where biodegradability is a large concern such as medicine.

Outline a method of determining the presence of heavy metals in a sample.

I think they already have done genetic engineering - they transferred the gene for the production of Biopol to the bacterium Escherichia Coli, since scientists can more easily work this more familiar bacterium, and it produces at a much faster rate. Also, they added propanoic acid to increase flexibility of the biopolymer produced.

 

[Azreil]

PS (for u non Physicists), the light released is quantised, hence the 'line' spectra, and not continuous spectrum

i wont even go into how electrons exhibit wave-particle duality, or go into Pauli's exclusion principle or hesienberg's uncertainty principle

...lol, good stuff...quantum physics...i miss it already

Pauli's exclusion principle! That's it! I knew I knew the name of it! =D

...That question can't be asked in the exam, can it? D:

I think they already have done genetic engineering - they transferred the gene for the production of Biopol to the bacterium Escherichia Coli, since scientists can more easily work this more familiar bacterium, and it produces at a much faster rate. Also, they added propanoic acid to increase flexibility of the biopolymer produced.

Oh okay, thanks for the information. =] Textbook = not the latest developments >>

 

[JasonNg1025]

Not in chem I hope

 

[danz90]

lol well the furtherst I think they want you to know is that different metals emit light of different wavelengths (due to atomic radii diferences), thats about it.

 

[old.skool.kid]

Quantitative: Relating to amount of substance
Qualitative: Relating to chemical/physical properties

HSC 05:

Assess the impact of the recent development of a named biopolymer on society and the environment.

PHB has the potential to replace polypropelene, due to its similar properties. It is waterproof, transparent, lightweight and can be used to produce platic bags, medical supplies, shampoo bottle etc. The advantage of this polymer is that is is biodegradable, does not release harmful toxins and is a renewable resource. However there is currently not enough technolgy to mass produce at a sufficient rate and compared to polypropolene it is about 5 times more expensive to manufacture. Although there have recently been new developments using genetic engeneering techniques allowing the production to be cheaper, PHB has not yet had a significant on the society and the environment. However it has massive potential.


Next Question: Describe the process of eutrophication, and asses the suitability of water quality tests uses to monitor it.

 

[JasonNg1025]

any more questions? I'm getting a little sick of chem cause that's what I've been trying to study for the past... I don't know. Not that I know everything, it's just that I'm not really too sure how to go about it now ><

 

[Azreil]

I think they already have done genetic engineering - they transferred the gene for the production of Biopol to the bacterium Escherichia Coli, since scientists can more easily work this more familiar bacterium, and it produces at a much faster rate. Also, they added propanoic acid to increase flexibility of the biopolymer produced.

Wait.

So does that mean Biopol is

[-O-CH-CO-CH<SUB>3</SUB>CH<SUB>2</SUB>CO-] n
___CH2

?

So I'd be wrong to call it PHB?

NEXT!
Assess the effect of the industrialisation of the Haber process.

 

[danz90]

Wait.

So does that mean Biopol is

[-O-CH-CO-CH<SUB>3</SUB>CH<SUB>2</SUB>CO-] n
___CH2

?

So I'd be wrong to call it PHB?

NEXT!
Assess the effect of the industrialisation of the Haber process.

I'm not sure, my chosen biopolymer isn't Biopol (I'm doing Cyclodextrin).. I just know some recent developments in Biopol.

 

[danz90]

Identify the name of the ester below, and the reactants used to produce it.