Question Chain Thread !!! (2 Viewers)

[imqt]

guys im having trouble converting grams to ppm, this is the first time ive encountered this question as we never learnt it... the 2007 paper was hell for me...can someone please exaplain this (DANZ? =)

 

[JasonNg1025]

Try this. It's got some answers that I wrote for some 2007 questions, and it includes one question on grams to ppm.

 

[imqt]

Try this. It's got some answers that I wrote for some 2007 questions, and it includes one question on grams to ppm.

thankyou il have a look

 

[axlenatore]

[FONT='Cambria','serif']Outline the role of a named chemist in a named industry and identify the branch of chemistry they are involved in and explain the chemical principles they use.[/FONT]

 

[aussiechick007]

[FONT='Cambria','serif']Outline the role of a named chemist in a named industry and identify the branch of chemistry they are involved in and explain the chemical principles they use.[/font]

A pharmicist in the industry of medicine has the role of dispensing medical drugs, is involved in the pharmacy branch of chemistry, and the chemical principle they use is the effect of medicines on the human body. They must have a knowledge of the workings of the human body so that no one is harmed.

crap answer i know but oh well i tried lol

Describe the physical and chemical processes needed to purify and sanitise a town water supply. (5 marks)

 

[danz90]

guys im having trouble converting grams to ppm, this is the first time ive encountered this question as we never learnt it... the 2007 paper was hell for me...can someone please exaplain this (DANZ? =)

Just remember that ppm is the same as mg/L or mg/kg.

So, for example if your given concentration as 0.15g/L
Then that would be 150mg/L --> 150ppm

But more likely you will have to convert mol/L to ppm.

to convert mol/L to g/L you MULTIPLY by the MOLAR MASS of the substance being measured.
eg. [SO₂]= 0.05mol/L
0.05 x (32.07 + 16 + 16) = 3.2035g/L
thats 3204mg/L, therefore 3204ppm.

To go back from g/L to mol/L you DIVIDE by the MOLAR MASS of the substance being measured.

Also, simple fact: 1g = 1000mg
and 1mg = 1000μg (micrograms)

hope that helps

 

[axlenatore]

A pharmicist in the industry of medicine has the role of dispensing medical drugs, is involved in the pharmacy branch of chemistry, and the chemical principle they use is the effect of medicines on the human body. They must have a knowledge of the workings of the human body so that no one is harmed.

crap answer i know but oh well i tried lol

Describe the physical and chemical processes needed to purify and sanitise a town water supply. (5 marks)

i had this for the chemist


Burhan Gemikonakli is a Plant Chemist at Qenos which is a major Australian chemical manufacturing company, which produces ethylene from ethane in order to polymerise it into polyethylene. Though not all of the ethylene produced is used for polymerisation, with Qenos selling some of it to a corporation on the same site who use it to form raw materials for other products. He works as an analytical chemist, which is a part of chemistry which is concerned with determining what substances and how much are present in certain materials.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>
<o> </o>
Burhan’s job is made up of several components, firstly it’s his job to monitor the quality of the ethylene products from the plant to ensure that they meet the requirements, and also determining what nature and amount the impurities present. Secondly he has the monitor the waste water from the complex to ensure that it meets environmental standards including pH, sulfate levels, and suspended solids. The final aspect of his job is working in collaborating with process engineers at the cracking furnace, monitoring and adjusting the operating conditions to optimise ethylene yield.<o></o>
<o> </o>
As an analytical chemist its Burhan’s job to determined how much of certain substances are present in material, so of the techniques he uses to do this includes gas chromatography which is a technique that passes a vaporized mixture into a flow of helium which passes over a solid, or liquid coated solid. The chemical principles which gas chromatography tests are adsorption (if a solid is used) or solubility (it its liquid). When using the principle of absorption the mixture is passed over a stationary solid, which absorb onto the surface of the solid to differing extents, thereby passing through the column at different rate, separating them. If the stationary phase is a liquid then the components of the mixture will dissolve into it to different extents, depending normally on polarity, as if the stationary liquid is polar it’s more likely to dissolve polar substances. It’s this dissolving which slows down the movements of certain components of the mixture thereby separating them.<o></o>

 

[danz90]

I'm still perplexed as to why people are still thinking you need to have a NAMED practising scientist. The exact syllabus dot points are:

- Outline the role of a chemist employed in a named industry or enterprise, identifying the branch of chemistry undertaken by the chemist and explaining a chemical principle that the chemist uses.

-Gather, process and present information from secondary sources about the work of practising scientists identifying:
- The variety of chemical occupations
- A specific chemical occupation for a more detailed study.

To me, personally, it doesn't say that you have to know the name of a practising scientist, but know about the role of a type of chemist in a particular industry (eg plastics industry) and what chemical principles they use.
Although, just in case, I might look up a particular practising scientist, just to confirm that dotpoint with secondary sources.

Last night when I called the HSC Advice line, they said that you don't really need to know the name of a practising scientist - basically what they want u to learn is the chemical principles a type of chemist employed in a named industry uses.

Will call again tonight tho, for another opinion. But then again, don't think this will be asked this year since it was in last year's paper. lol better not jinx it, might be like a 5 or 6 marker this time round LOL
More likely that Combustion will be something they might ask from that part of the M&M module.

 

[Azreil]

Describe the physical and chemical processes needed to purify and sanitise a town water supply. (5 marks)

Flocculation: the addition of Fe3+ ions flocculates any particulates, creating larger particles and encouraging solids to fall to the bottom by increasing their density. This is also assisted by the water being stored for a period od time and hence the particles "clumping up" over time.
Filtration: This generally occurs through sand. This removes any large particles and allows only water without contaminants through. At houses, this may instead consist of the use of membrane filters however on a large scale these are generally seen as too expensive and the cost is not offset by a large increase in effectiveness.
Sanitation: By bubbling Cl(g) through the water, the following occurs:
Cl2 (g) + H2O(l) -> HCl + HOCl
HOCl <-> H+ + OCl-
OCl- is poisonous to bacteria and hence the use of Cl in the sanitation of town water is highly effective. It did not, however, protect Sydney from the giardia outbreak of 1998. Ozone is seen as more effective, however, similar to membrane filters the increase in cost does not offset the increase in effectiveness.
Addition of fluoride: While not essential, many water supplies add fluoride to their water. This is to assist in the health of those who drink it as fluoride is generally deficient in the diet and is essential to the maintenance of dental health.

Describe a test that could quantitatively monitor the concentration of phosphate ions in a water supply.

 

[imqt]

Just remember that ppm is the same as mg/L or mg/kg.

So, for example if your given concentration as 0.15g/L
Then that would be 150mg/L --> 150ppm

But more likely you will have to convert mol/L to ppm.

to convert mol/L to g/L you MULTIPLY by the MOLAR MASS of the substance being measured.
eg. [SO₂]= 0.05mol/L
0.05 x (32.07 + 16 + 16) = 3.2035g/L
thats 3204mg/L, therefore 3204ppm.

To go back from g/L to mol/L you DIVIDE by the MOLAR MASS of the substance being measured.

Also, simple fact: 1g = 1000mg
and 1mg = 1000μg (micrograms)

hope that helps

you're fantastic thankyou!

 

[imqt]

hey anyone know how you can use CALORIMETRY as a method of testing for heavy metals and eutrophication?

 

[axlenatore]

I'm still perplexed as to why people are still thinking you need to have a NAMED practising scientist. The exact syllabus dot points are:

- Outline the role of a chemist employed in a named industry or enterprise, identifying the branch of chemistry undertaken by the chemist and explaining a chemical principle that the chemist uses.

-Gather, process and present information from secondary sources about the work of practising scientists identifying:
- The variety of chemical occupations
- A specific chemical occupation for a more detailed study.

To me, personally, it doesn't say that you have to know the name of a practising scientist, but know about the role of a type of chemist in a particular industry (eg plastics industry) and what chemical principles they use.
Although, just in case, I might look up a particular practising scientist, just to confirm that dotpoint with secondary sources.

Last night when I called the HSC Advice line, they said that you don't really need to know the name of a practising scientist - basically what they want u to learn is the chemical principles a type of chemist employed in a named industry uses.

Will call again tonight tho, for another opinion. But then again, don't think this will be asked this year since it was in last year's paper. lol better not jinx it, might be like a 5 or 6 marker this time round LOL
More likely that Combustion will be something they might ask from that part of the M&M module.

The dot point is actually
[FONT='Cambria','serif'](1-i) [/FONT][FONT='Cambria','serif']Outline the role of a named chemist in a named industry and identify the branch of chemistry they are involved in and explain the chemical principles they use.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>[/FONT]

 

[danz90]

Flocculation: the addition of Fe3+ ions flocculates any particulates, creating larger particles and encouraging solids to fall to the bottom by increasing their density. This is also assisted by the water being stored for a period od time and hence the particles "clumping up" over time.
Filtration: This generally occurs through sand. This removes any large particles and allows only water without contaminants through. At houses, this may instead consist of the use of membrane filters however on a large scale these are generally seen as too expensive and the cost is not offset by a large increase in effectiveness.
Sanitation: By bubbling Cl(g) through the water, the following occurs:
Cl2 (g) + H2O(l) -> HCl + HOCl
HOCl <-> H+ + OCl-
OCl- is poisonous to bacteria and hence the use of Cl in the sanitation of town water is highly effective. It did not, however, protect Sydney from the giardia outbreak of 1998. Ozone is seen as more effective, however, similar to membrane filters the increase in cost does not offset the increase in effectiveness.
Addition of fluoride: While not essential, many water supplies add fluoride to their water. This is to assist in the health of those who drink it as fluoride is generally deficient in the diet and is essential to the maintenance of dental health.

Describe a test that could quantitatively monitor the concentration of phosphate ions in a water supply.

I'm thinking maybe a precipitation reaction with Mg(NO₃)₂. Since Mg₃(PO₄)₂ is an insoluble precipitate.
Procedure would be:

-Obtain a 100mL water sample (made up of mixed smaller samples from different areas of the water supply).

- Add excess HCl to ensure that any carbonate ions are removed from the sample. If any white precipitate (most likely Lead Chloride) is formed, pass the solution through a filter paper until all precipitate (if any) is removed, and then collect the filtrate.

- Add Excess Mg(NO₃)₂ solution until no more precipitate is formed.

- Preweigh the filter paper that is going to be used.

- Pass the mixture through the filter paper (using a funnel), ensuring all precipitate has been collected.

- Dry the filter paper+precipitate to constant mass (to ensure all water has been removed).

-Weigh the filter paper+precipitate. Then, minus the original mass of the filter paper to obtain an accurate mass of the Mg₃(PO₄)₂ solid.

-mass of PO₄^3- is determined by multiplying the mass of the solid by 0.7962 (pre-calculated from periodic table).
Eg, mass of solid is 1.50g
therefore, mass of phosphate ions = 1.19g

concentration of phosphate: 1.19g/100mL

= 11.9g/L

= 11900mg/L

= 11.9 x 10³ ppm

This procedure should be repeated at regular weekly intervals to monitor concentration of PO₄^3- in a water supply.

 

[danz90]

The dot point is actually
[FONT='Cambria','serif'](1-i) [/font][FONT='Cambria','serif']Outline the role of a named chemist in a named industry and identify the branch of chemistry they are involved in and explain the chemical principles they use.fficeffice" /><O></O>[/font]

 

[JasonNg1025]

I'm thinking maybe a precipitation reaction with Mg(NO₃)₂. Since Mg₃(PO₄)₂ is an insoluble precipitate.
Procedure would be:

-Obtain a 100mL water sample (made up of mixed smaller samples from different areas of the water supply).

- Add excess HCl to ensure that any carbonate ions are removed from the sample. If any white precipitate (most likely Lead Chloride) is formed, pass the solution through a filter paper until all precipitate (if any) is removed, and then collect the filtrate.

- Add Excess Mg(NO₃)₂ solution until no more precipitate is formed.

- Preweigh the filter paper that is going to be used.

- Pass the mixture through the filter paper (using a funnel), ensuring all precipitate has been collected.

- Dry the filter paper+precipitate to constant mass (to ensure all water has been removed).

-Weigh the filter paper+precipitate. Then, minus the original mass of the filter paper to obtain an accurate mass of the Mg₃(PO₄)₂ solid.

-mass of PO₄^3- is determined by multiplying the mass of the solid by 0.7962 (pre-calculated from periodic table).
Eg, mass of solid is 1.50g
therefore, mass of phosphate ions = 1.19g

concentration of phosphate: 1.19g/100mL

= 11.9g/L

= 11900mg/L

= 11.9 x 10³ ppm

This procedure should be repeated at regular weekly intervals to monitor concentration of PO₄^3- in a water supply.

Umm my notes say you can use ammonium molybdate as well
Forms a bright yellow precipitate. You can keep that in mind in case it's a multiple choice or something

 

[danz90]

Umm my notes say you can use ammonium molybdate as well
Forms a bright yellow precipitate. You can keep that in mind in case it's a multiple choice or something

kk cool thanx for the tip i've never heard of that one before

 

[gcmk]

I'm still perplexed as to why people are still thinking you need to have a NAMED practising scientist. The exact syllabus dot points are:

- Outline the role of a chemist employed in a named industry or enterprise, identifying the branch of chemistry undertaken by the chemist and explaining a chemical principle that the chemist uses.

-Gather, process and present information from secondary sources about the work of practising scientists identifying:
- The variety of chemical occupations
- A specific chemical occupation for a more detailed study.

To me, personally, it doesn't say that you have to know the name of a practising scientist, but know about the role of a type of chemist in a particular industry (eg plastics industry) and what chemical principles they use.
Although, just in case, I might look up a particular practising scientist, just to confirm that dotpoint with secondary sources.

Last night when I called the HSC Advice line, they said that you don't really need to know the name of a practising scientist - basically what they want u to learn is the chemical principles a type of chemist employed in a named industry uses.

Will call again tonight tho, for another opinion. But then again, don't think this will be asked this year since it was in last year's paper. lol better not jinx it, might be like a 5 or 6 marker this time round LOL
More likely that Combustion will be something they might ask from that part of the M&M module.

would it be okay if we chose a analytical chemist who uses chemical principles relating to le chatelier's principle and equilibrium to synthesise ammonia? can't we use the knowledge from other syllabus points?

 

[eddy11]

hey anyone know how you can use CALORIMETRY as a method of testing for heavy metals and eutrophication?

dunno about calorimetry which measures energy, but colourimetry on the other hand...

Eutrophication is the enrichment of a water way with excessive nutrients, namlely phospate and nitrate.
The soluble nitrate content of a water sample can be determined instrumentally using a colourimeter. The nitrate ions react with a reductant to convert them to nitrite ions which react with a reagent to produce a pink-purple dye that is measured against known standards
produce a pink-purple azo-dye that is measured
colourimetrically against known standards.

As for heavy metals and phosphate i suppose it would be a similar process

In my opinion i think that flow injection analysis is a better method at testing for heavy metals and eutrophication, some FI analysers can measure down to 15ppb and they can detect multiple ions (cations and anions) either simultaneously or in quick sucession

 

[JasonNg1025]

would it be okay if we chose a analytical chemist who uses chemical principles relating to le chatelier's principle and equilibrium to synthesise ammonia? can't we use the knowledge from other syllabus points?

Yes that's what I've been wondering too. In another practice paper, for that type of question I wrote someone dealing with the Haber process, but the answers were pretty vague. Could anyone shed a little light on this area?

 

[danz90]

would it be okay if we chose a analytical chemist who uses chemical principles relating to le chatelier's principle and equilibrium to synthesise ammonia? can't we use the knowledge from other syllabus points?

Of course you can

The example I usually use is an organic or industrial chemist employed in the plastic industry. This chemist carries out quality control testing on plastics produced, such as LDPE and HDPE, by measuring density of certain plastics to examine the level/extent of branching and aligning of monomers.

I've just used knowledge from Production of Materials.

Edit: I told the guy on the advice line this last night, and he said that's fine. That's all you would need to write for a 2 or 3 marker. you don't really need to name a practising scientist, according to him (although im getting a second opinion tonight).