Predictions for Chemistry 2014 HSC? (9 Viewers)

[SuchSmallHands]

It's not portable.
Other advantages include -
- Measure the concentration of metal up to parts per billion
- Can measure the concentration of heavy metals such as lead, cadmium, mercury in water, air or soil. Results could be used by individuals to determine the severity of the pollution and to act on it accordingly.
- The advent of this technology has provided information about trace elements, which was something scientists did not fathom as gravimetric analysis (wet methods) was innaccurate.
- The advent of this technology has not only saved the lives of humans, but also the Australian agricultural industry, estimated to be worth $32 billion. AAS, has enabled scientists to comprehend that soil also require trace elements such as cobalt and other essential nutrients in order to allow for crop growth.
- other metal ions in a solution will not interfere

Disadvantages -
- The use of this technology is expensive
- scientists must know what metal they are testing for before using the machine
- very long process
- involves making numerous standard solutions to calibrate the machine
- can only test one metal at a time.
- scientists must know

It can be http://www.labmate-online.com/news/...spectrometer_with_innovated_technology/17937/

 

[SuchSmallHands]

goodnight friends. i will hibernate now

Goodnight!

 

[faisalabdul16]

It can be http://www.labmate-online.com/news/...spectrometer_with_innovated_technology/17937/

Interesting! Thanks for that

 

[SuchSmallHands]

Interesting! Thanks for that

It looks like a pretty recent development, there don't seem to be too many of them for sale. From the looks of this http://www.opticsinfobase.org/as/abstract.cfm?uri=as-50-2-174 it was only first developed around 18 years ago, so probably only just being used generally now (ie. after most textbooks and resources were written).

 

[SuchSmallHands]

Outline a way in which a student could determine the phosphate and nitrate levels of water (4 marks)

 

[pheelx3]

Outline a way in which a student could determine the phosphate and nitrate levels of water (4 marks)

Monitoring nitrate:
Pass the sample through of granulated Cd/Cu which reduces the nitrate to nitrite
Then add certain reagents to form an azo-dye of pink/purple colour
Then determine concentration of NO3- relative to standards

Monitoring phosphate:
Add acidified ammonium molybdate -> a yellow precipitate will form if phosphate is present
Then add ascorbic acid, which redissolves the precipitate by forming an intense blue complex ion
Determine concentration of PO43- relative to standards

Pretty shitty response I know...
I don't exactly understand the Kjeldahl method if someone could explain?
Convert N to NH4(SO4)2 by adding H2SO4
Add base to form NH3, and remove by distillation
Add excess acid then back titrate with standard sodium carbonate... hmm... yeah no i dont understand

 

[SuchSmallHands]

I don't exactly understand the Kjeldahl method if someone could explain?
Convert N to NH4(SO4)2 by adding H2SO4
Add base to form NH3, and remove by distillation
Add excess acid then back titrate with standard sodium carbonate... hmm... yeah no i dont understand

I think you mean (NH4)2SO4, but yeah. You can also do it with direct titration with boric acid, rather than back titration. What exactly don't you get? You add H2SO4 to make (NH4)2SO4, you add excess base to get NH3, you distill the NH3 and titrate it to work out how many miles of ammonia you got. From there you work out how many moles of nitrogen you had in the water, then you put that over the volume of water for concentration. I don't know why you're stressing about this anyway, it's not in our syllabus so while it can occasionally help to know, you'll never be directly tested on it.

 

[faisalabdul16]

 

[pheelx3]

you're a cunt

Microscopic membrane filters are not commonly used for the treatment of water in Sydney (with the exception of olympic park and newton). These membrane filters come in two types: capillary membrane filters and pleated membrane sheets. Both are made with a polymer (typically PTFE) and have holes punctured within them of typically 0.2 micrometers.
Capillary membrane filters are quite like straws. Their outer diameter is about 100 micrometers, and water is pumped in from the inside parallel to the membrane direction. This allows for high pressures to be used. Similarly, pleated membrane filters are made of a polymer sheet with holes puntured. This is pleated effectively giving an increased SA. The water is also pumped perpendicular to the pores, allowing for very high pressured to be used without clogging. Both are effective filtering out small particles, such as microbes that wouldn't be killed by clorination (e.g. Gardia which was present in the 1998 sydney water crisis). Also black flushing can be done to clean the filters, allowing for the filter to be reused for a long period of time. However, a disadvantage would be that larger particles still need to be removed before water is pumped through the filter. It is also very expensive to manufacture, and current methods are sufficient in meeting ADWG standards, and hence the use of microscopic membrane filters is currently unjustified.

 

[enigma_1]

you're a cunt

Microscopic membrane filters are not commonly used for the treatment of water in Sydney (with the exception of olympic park and newton). These membrane filters come in two types: capillary membrane filters and pleated membrane sheets. Both are made with a polymer (typically PTFE) and have holes punctured within them of typically 0.2 micrometers.
Capillary membrane filters are quite like straws. Their outer diameter is about 100 micrometers, and water is pumped in from the inside parallel to the membrane direction. This allows for high pressures to be used. Similarly, pleated membrane filters are made of a polymer sheet with holes puntured. This is pleated effectively giving an increased SA. The water is also pumped perpendicular to the pores, allowing for very high pressured to be used without clogging. Both are effective filtering out small particles, such as microbes that wouldn't be killed by clorination (e.g. Gardia which was present in the 1998 sydney water crisis). Also black flushing can be done to clean the filters, allowing for the filter to be reused for a long period of time. However, a disadvantage would be that larger particles still need to be removed before water is pumped through the filter. It is also very expensive to manufacture, and current methods are sufficient in meeting ADWG standards, and hence the use of microscopic membrane filters is currently unjustified.

harsh.


The point of this is to post hard/annoying questions anyway.

Perhaps you could make the advantages, disadvantages and evaluation more evident. Overall good. Mention the process of reverse osmosis, and that MMF is used in public swimming pools because it is expensive.

Also, you should probably say the Sydney water 1998 thing meant that chlorination itself was not effective, thus MMF was developed as an alternative because it gets rid of these protozoans (Cryptosporidium and Giardia) which contaminated Sydney water 1998. I would probably have said this at the start to give a sort of background to your answer.

Furthermore, MMF would be impractical to use for water with sewage because the sewage would clog up the pores. The smaller the pores,, the more expensive the MMF.

 

[faisalabdul16]

you're a cunt

Microscopic membrane filters are not commonly used for the treatment of water in Sydney (with the exception of olympic park and newton). These membrane filters come in two types: capillary membrane filters and pleated membrane sheets. Both are made with a polymer (typically PTFE) and have holes punctured within them of typically 0.2 micrometers.
Capillary membrane filters are quite like straws. Their outer diameter is about 100 micrometers, and water is pumped in from the inside parallel to the membrane direction. This allows for high pressures to be used. Similarly, pleated membrane filters are made of a polymer sheet with holes puntured. This is pleated effectively giving an increased SA. The water is also pumped perpendicular to the pores, allowing for very high pressured to be used without clogging. Both are effective filtering out small particles, such as microbes that wouldn't be killed by chlorination (e.g. Giardia which was present in the 1998 sydney water crisis). Also back flushing can be done to clean the filters, allowing for the filter to be reused for a long period of time. However, a disadvantage would be that larger particles still need to be removed before water is pumped through the filter. It is also very expensive to manufacture, and current methods are sufficient in meeting ADWG standards, and hence the use of microscopic membrane filters is currently unjustified.

Is the red part your evaluation?

 

[pheelx3]

harsh.

Haha... Sorry. It's just I said the said the same thing when it came up in the HSC last year or whatever year it was.

Mention the process of reverse osmosis, and that MMF is used in public swimming pools because it is expensive.

Noted. Cheers

Also, you should probably say the Sydney water 1998 thing meant that chlorination itself was not effective, thus MMF was developed as an alternative because it gets rid of these protozoans (Cryptosporidium and Giardia) which contaminated Sydney water 1998. I would probably have said this at the start to give a sort of background to your answer.

Furthermore, MMF would be impractical to use for water with sewage because the sewage would clog up the pores. The smaller the pores,, the more expensive the MMF.

I think I mentioned this of these implicitly: "microbes that wouldn't be killed by clorination (e.g. Gardia which was present in the 1998 sydney water crisis)" and then the clogging up of pores: "Also black flushing can be done to clean the filters"

But thanks for the feedback nonetheless.

[/I]

Is the red part your evaluation?

Yeah is it too superficial?

 

[faisalabdul16]

Haha... Sorry. It's just I said the said the same thing when it came up in the HSC last year or whatever year it was.
Noted. Cheers
I think I mentioned this of these implicitly: "microbes that wouldn't be killed by clorination (e.g. Gardia which was present in the 1998 sydney water crisis)" and then the clogging up of pores: "Also black flushing can be done to clean the filters"
But thanks for the feedback nonetheless.
Yeah is it too superficial?

It's hard to tell whether it is an evaluation or not. Because the first half of the sentence, the marker could argue that you're stating an disadvantage, and then the last half of the sentence is very small and not a proper evaluating statement.

Imo, just at the end give like a 2 or 3 line evaluation.

 

[enigma_1]

Haha... Sorry. It's just I said the said the same thing when it came up in the HSC last year or whatever year it was.


Noted. Cheers


I think I mentioned this of these implicitly: "microbes that wouldn't be killed by clorination (e.g. Gardia which was present in the 1998 sydney water crisis)" and then the clogging up of pores: "Also black flushing can be done to clean the filters"

But thanks for the feedback nonetheless.




Yeah is it too superficial?

No worries I know you're gonna hate this, but to maximise your marks always be explicit in chem. I know you know, but the marker doesn't. Pretend like the marker is an idiot and you'll get the marks guaranteed. I lost heaps of marks in trial for being subtle so I've learnt not to do so.

 

[pheelx3]

It's hard to tell whether it is an evaluation or not. Because the first half of the sentence, the marker could argue that you're stating an disadvantage, and then the last half of the sentence is very small and not a proper evaluating statement.

Imo, just at the end give like a 2 or 3 line evaluation.

Haha I'll keep that in mind, thank you. (are HSC markers such cunts?!)

No worries I know you're gonna hate this, but to maximise your marks always be explicit in chem. I know you know, but the marker doesn't. Pretend like the marker is an idiot and you'll get the marks guaranteed. I lost heaps of marks in trial for being subtle so I've learnt not to do so.

Yeah so did I.. looks like I haven't learnt my lessons, though
Next question? :L

 

[faisalabdul16]

Haha I'll keep that in mind, thank you. (are HSC markers such cunts?!)





Yeah so did I.. looks like I haven't learnt my lessons, though
Next question? :L

HSC markers are worse than cunts. Someone else post a question, this time i also want to have a go

 

[QZP]

You guys sleep later than me AND wake up earlier. Awks. What am I doing with my life

 

[enigma_1]

You guys sleep later than me AND wake up earlier. Awks. What am I doing with my life

It's fine The key to looking younger longer is to sleep more.

 

[QZP]

How is photochemical smog formed and what does it consists of?

- Toxic, brown haze mixture consisting of ozone, NOx and VOCs formed by action of sunlight on pollutants (NOx and VOCs)
- (Insert equation for formation of ozone from NO2)

Is this correct? Or should I say NO2 and VOCs instead of NOx and VOCs

Anything else to add? (I know so less about photochemical smog).

 

[faisalabdul16]

You guys sleep later than me AND wake up earlier. Awks. What am I doing with my life

Hahaha, i slept at 2, woke up 8:30.

It's not good, because i only had 4 hours sleep :[ the other 2 and a half hours were literally me not falling asleep

But then for some reason i am not tired as well