Predictions for Chemistry 2014 HSC? (2 Viewers)

[photastic]

Yeah it bioaccumulates in organisms once consumed and makes it way up the food chain causing harm. Etc

Biology student

 

[faisalabdul16]

Biology student

Indeed

My teacher said you can incorporate information from other sciences. For instance the need of trace elements can be linked to enzyme activity and how if certain vital elements are missing, enzyme activity can be significantly reduced and as a result, metabolic functioning begins to slow down and then the person is screwed.

 

[photastic]

fasabualsaisabuld

you seem so prepared for chemistry good job man haha

State rank

 

[faisalabdul16]

fasabualsaisabuld

you seem so prepared for chemistry good job man haha

haha yeah my plans where to finish revision for all subjects this week, leaving me two weeks of nothing but papers and essays.

 

[faisalabdul16]

State rank

naooo the QZP guy will.

Next question:

Describe the process of eutrophication, and assess the suitability of water quality tests used to monitor it.

 

[Speed6]

Another Question:

 

[faisalabdul16]

naooo the QZP guy will.

Next question:

Describe the process of eutrophication, and assess the suitability of water quality tests used to monitor it.

I'll answer my own question since no one else is bothering #sadlyf

Eutrophication is a process which results in large algal blooms in water ways due to excess nutrients such as nitrogen and phosphorus being present. Algae forms on the surface of water and reproduces exponentially, causing the dissolved oxygen levels of water to reduce dramatically as algae blocks sunlight from entering the water and allowing plants in the water to photosynthesise. Dissolved oxygen levels also decrease as algae undergoes respiration at night. After the nutrients have been used up, the algae die and anaerobic bacteria move in and decompose the organic matter while producing detrimental toxins. Suitable water tests to monitor the quality of the water include monitoring dissolved oxygen concentrations along with BOD. Measuring the dissolved oxygen concentration is a suitable test as there is often a clear reason as to why dissolved oxygen concentration in water is dramatically low, most likely because of the presence of algae. Therefore, monitoring and testing dissolved oxygen concentrations is suitable as it provides individuals with adequate information about the reason as to why there may be a low concentration. Furthermore, measuring BOD levels is also a suitable form of testing because BOD levels would be high due to the presence of bacteria, trying to not only break down the organic waste of fish, but also the algae as nutrients run out and the algae begin to die. BOD levels would be significantly high if eutrophication were to occur, and therefore monitoring and testing levels of BOD is suitable as it would allow individuals to determine whether eutrophication is occurring or about to occur in water.

Colorimetric testing as well but ceebs explaining

Another Question:

Dislike this question haha

 

[QZP]

I don't think DO/BOD is a valid measurement of eutrophication because it is affected by too many variables other than phosphorous/nitrogen content i.e. algae activity. Do you have a source?? I havn't been doing any chem lately so I might be wrong :X

 

[faisalabdul16]

I don't think DO/BOD is a valid measurement of eutrophication because it is affected by too many variables other than phosphorous/nitrogen content i.e. algae activity. Do you have a source?? I havn't been doing any chem lately so I might be wrong :X

HSC online says DO is a valid measurement, so does my tutor and teacher at school.
http://hsc.csu.edu.au/chemistry/core/monitoring/chem945/945net.html#net1

Were you expecting measuring the concentration of nitrogen and phosphorus and if they N is greater than 10:1 it is safe and if not then eutrophication can or is occuring.

Bold part - algae activity indicates that eutrophication is occuring? It is because of excess nitrogen and phosphorus that results in algal blooms which causes DO levels to decrease and BOD levels to increase. Why isn't that a valid measurement?

 

[faisalabdul16]

Also just sent a text to my teacher and she said that DO and BOD are suitable tests.

 

[QZP]

HSC online says DO is a valid measurement, so does my tutor and teacher at school.
http://hsc.csu.edu.au/chemistry/core/monitoring/chem945/945net.html#net1

Were you expecting measuring the concentration of nitrogen and phosphorus and if they N is greater than 10:1 it is safe and if not then eutrophication can or is occuring.

Bold part - algae activity indicates that eutrophication is occuring? It is because of excess nitrogen and phosphorus that results in algal blooms which causes DO levels to decrease and BOD levels to increase. Why isn't that a valid measurement?

Organic wastes from sewerage, agricultural run off, etc. also cause low DO and high BOD. Also, photosynthesis from aquatic plants affects DO.

Example scenario: TDS and turbidity of waterway is affected such that photosynthesis activity of aquatic plants is reduced. This leads to a decrease in DO. It would be incorrect to conclude that this was caused by eutrophication.

I just don't see how you can pin-point low DO and high BOD to eutrophication. :S Jacaranda has nothing about measuring eutrophication with DO/BOD but instead titration and colourimetry.

 

[faisalabdul16]

Organic wastes from sewerage, agricultural run off, etc. also cause low DO and high BOD. Also, photosynthesis from aquatic plants affects DO.

Example scenario: TDS and turbidity of waterway is affected such that photosynthesis activity of aquatic plants is reduced. This leads to a decrease in DO. It would be incorrect to conclude that this was caused by eutrophication.

I just don't see how you can pin-point low DO and high BOD to eutrophication. :S Jacaranda has nothing about measuring eutrophication with DO/BOD but instead titration and colourimetry.

Yes i agree that organic wastes etc cause low DO levels and high BOD. However, if eutrophication was to occur, photosynthesis would not occur in aqautic plants as algae remain at the surface of the water and block sunlight from entering the water. IF somehow they are able to undergo photosynthesis, it would not make a significant change in DO levels as algae and the plants undergo respiration at night, decreasing DO levels dramatically. Algae also reproduce exponentially and really quickly therefore will be lots and lots of algae present.

Bold part - Reduced photosynthesis is yes because of the water being turbid and it is turbid because of eutrophication. It's because of the algae that the water is turbid. Algae settles on the surface of water and acts as a barrier, preventing light from entering.

If you were to bring in other factors, then all tests are not suitable except for directly measuring nitrogen and phosphorus levels. And if the nitrogen to phosphorus ratio is greater than 10:1, then it is safe.


The italicised part would then be the ONLY suitable way of testing for eutrophication.

 

[QZP]

Yes i agree that organic wastes etc cause low DO levels and high BOD. However, if eutrophication was to occur, photosynthesis would not occur in aqautic plants as algae remain at the surface of the water and block sunlight from entering the water. IF somehow they are able to undergo photosynthesis, it would not make a significant change in DO levels as algae and the plants undergo respiration at night, decreasing DO levels dramatically. Algae also reproduce exponentially and really quickly therefore will be lots and lots of algae present.

Bold part - Reduced photosynthesis is yes because of the water being turbid and it is turbid because of eutrophication. It's because of the algae that the water is turbid. Algae settles on the surface of water and acts as a barrier, preventing light from entering.

If you were to bring in other factors, then all tests are not suitable except for directly measuring nitrogen and phosphorus levels. And if the nitrogen to phosphorus ratio is greater than 10:1, then it is safe.


The italicised part would then be the ONLY suitable way of testing for eutrophication.

BOLD: Yes I've been saying that considering other factors, then measurement of DO/BOD is not valid for purposes of monitoring eutrophication (which is the Q).

Correct me if I'm wrong, but your method (measuring significant low DO and high BOD) only indicates algal blooms. How is that monitoring eutrophication? If you instead measure minimal low DO and high BOD then this is unreliable to monitor eutrophication progress due to the external factors as I have mentioned that may affect DO and BOD. (What I'm trying to show is that both significant/low changes in DO/BOD are not very good for monitoring eutrophication which is what you were trying to talk about or something)

Usually we monitor something so we can prevent problems. By direct measurements of nitrogen/phosphate content using e.g. colourimetry we can measure their exact concentrations and thus the extent of eutrophication.

Btw I did a quick check on conq. chem also and they say the same thing as jacaranda (there is no mention of using measurements of DO and BOD for monitoring eutrophication)

 

[faisalabdul16]

BOLD: Yes I've been saying that considering other factors, then measurement of DO/BOD is not valid for purposes of monitoring eutrophication (which is the Q).

Correct me if I'm wrong, but your method (measuring significant low DO and high BOD) only indicates algal blooms. How is that monitoring eutrophication? If you instead measure minimal low DO and high BOD then this is unreliable to monitor eutrophication progress due to the external factors as I have mentioned that may affect DO and BOD. (What I'm trying to show is that both significant/low changes in DO/BOD are not very good for monitoring eutrophication which is what you were trying to talk about or something)

Usually we monitor something so we can prevent problems. By direct measurements of nitrogen/phosphate content using e.g. colourimetry we can measure their exact concentrations and thus the extent of eutrophication.

Btw I did a quick check on conq. chem also and they say the same thing as jacaranda (there is no mention of using measurements of DO and BOD for monitoring eutrophication)

So colorimetric testing it is!

Thanks!

More questions!

I like these discussions! hahaha

 

[QZP]

Discussion is always good I wouldn't discount measuring DO/BOD entirely. I think it is often a "good" but not best measurement of eutrophication which is why you may see it as the answer in MCQ for measuring eutrophication. But in long responses, go with colourimetric analysis for reasons above (it is more reliable and direct). NICE! We cleared stuff up

 

[faisalabdul16]

Discussion is always good I wouldn't discount measuring DO/BOD entirely. I think it is often a "good" but not best measurement of eutrophication which is why you may see it as the answer in MCQ for measuring eutrophication. But in long responses, go with colourimetric analysis for reasons above (it is more reliable and direct). NICE! We cleared stuff up

Indeed we did and true!
Hmm

Discuss factors that must be considered when using neutralisation reactions to safely minimise damage in chemical spills.

 

[the wobbulator]

HSC online says DO is a valid measurement, so does my tutor and teacher at school.
http://hsc.csu.edu.au/chemistry/core/monitoring/chem945/945net.html#net1

Were you expecting measuring the concentration of nitrogen and phosphorus and if they N is greater than 10:1 it is safe and if not then eutrophication can or is occuring.

Bold part - algae activity indicates that eutrophication is occuring? It is because of excess nitrogen and phosphorus that results in algal blooms which causes DO levels to decrease and BOD levels to increase. Why isn't that a valid measurement?

It is 16:1 ratio of N (Pretty important to not get this wrong as my tutor who is a hsc marker and she take away marks for people not giving the correct details... SO watchout!!)
Also you have to be familiar with the kjedahl's method of determining total nitrogen content of the sample and for total phosphorous you need to learn about colorimetry which is quite similiar to AAS tbh...

BTW she took off marks to almost everyone perhaps not the state rankers in the 2009/2010 hsc exam (i'm not sure which one) for not writing the proper definition of BOD. She said they either missed the standard conditions or that they forgot to mention that BOD is the difference in dissolved oxygen concentration.... SO BASICALLY IN CHEM, YOU ARE LOSING MARKS AND YOU DON"T REALISE IT TAKE CAUTION !!!!!

 

[faisalabdul16]

It is 16:1 ratio of N (Pretty important to not get this wrong as my tutor who is a hsc marker and she take away marks for people not giving the correct details... SO watchout!!)
Also you have to be familiar with the kjedahl's method of determining total nitrogen content of the sample and for total phosphorous you need to learn about colorimetry which is quite similiar to AAS tbh...

BTW she took off marks to almost everyone perhaps not the state rankers in the 2009/2010 hsc exam (i'm not sure which one) for not writing the proper definition of BOD. She said they either missed the standard conditions or that they forgot to mention that BOD is the difference in dissolved oxygen concentration.... SO BASICALLY IN CHEM, YOU ARE LOSING MARKS AND YOU DON"T REALISE IT TAKE CAUTION !!!!!

Never learnt that wtf...

 

[QZP]

It is 16:1 ratio of N (Pretty important to not get this wrong as my tutor who is a hsc marker and she take away marks for people not giving the correct details... SO watchout!!)
Also you have to be familiar with the kjedahl's method of determining total nitrogen content of the sample and for total phosphorous you need to learn about colorimetry which is quite similiar to AAS tbh...

BTW she took off marks to almost everyone perhaps not the state rankers in the 2009/2010 hsc exam (i'm not sure which one) for not writing the proper definition of BOD. She said they either missed the standard conditions or that they forgot to mention that BOD is the difference in dissolved oxygen concentration.... SO BASICALLY IN CHEM, YOU ARE LOSING MARKS AND YOU DON"T REALISE IT TAKE CAUTION !!!!!

rofl mate

 

[Futuremedstudent]

definitely there will be some mole questions.