HSC 2012-2015 Chemistry Marathon (archive) (3 Viewers)

[Dylanamali]

Re: HSC 2012 Chemistry Marathon

Na2CO3 + 2HCl ---> 2NaCl + H2O + CO2

that's the equation. so yeah your right.. my bad, I wasn't looking at the question properly and only read off the answers.
so yeah that's correct.

So you haven't even learnt titrations yet? just read ahead, I presume?

 

[someth1ng]

Re: HSC 2012 Chemistry Marathon

Na2CO3 + 2HCl ---> 2NaCl + H2O + CO2

that's the equation. so yeah your right.. my bad, I wasn't looking at the question properly and only read off the answers.
so yeah that's correct.

So you haven't even learnt titrations yet? just read ahead, I presume?

Yeah, no biggie.

Our school hasn't done titrations yet but they give us 20 questions and 10 questions will be asked in the half yearly (calculations have different values) - I just wanted to know all the solutions so I could get all the notes ready since I know pretty much everything else already. The actual working doesn't seem so complicated after you understand what the question is asking and understanding all the jargon.

Time for me to go to sleep - my bed time is well overdue.
Goodnight, thanks for your help.

 

[Dylanamali]

Re: HSC 2012 Chemistry Marathon

ah right.. that's preety good then lol.
you can preety much prep yourself to get 100%

 

[Kimyia]

Re: HSC 2012 Chemistry Marathon

btw - just out of curiosity where is everyone at in the syllabus in HSC chem atm? how far into acidic are you guys?

^ sanjoy you already done esterification at school?? =O

We've finished production of materials but we're only up to the second dot point in acidic so I haven't got a clue about all these titrations lol

 

[Dylanamali]

Re: HSC 2012 Chemistry Marathon

We've finished production of materials but we're only up to the second dot point in acidic so I haven't got a clue about all these titrations lol

ahha yeah I wouldn't expect many schools to have done titrations at this stage..
probably a decent place to be at right now would be just finishing off Le Chatelier's principle and getting into the theory behind acids and bases - in terms of strength, concentration etc.

 

[someth1ng]

Re: HSC 2012 Chemistry Marathon

ahha yeah I wouldn't expect many schools to have done titrations at this stage..
probably a decent place to be at right now would be just finishing off Le Chatelier's principle and getting into the theory behind acids and bases - in terms of strength, concentration etc.

We're roughly around there.

 

[nightweaver066]

Re: HSC 2012 Chemistry Marathon

New question:

 

[viraj30]

Re: HSC 2012 Chemistry Marathon

what is the temperature and pressure in which high density polyethylene is made? (confused bcos in excel it says 'just above 300 celsius' whereas in KISS booklet it says at about 60 celsius..which ones correct..can it b a typo

 

[deswa1]

Re: HSC 2012 Chemistry Marathon

New question:

The properties of Technetium 99m make it very useful for its applications as a medical tracer in medicine. As it undergoes gamma decay (maybe write equation, but its only 3 marks), it can be placed inside the body effectively 'tagging' the required area. For example, it can be used to detect blood clots and brain tumours. Technetium 99m can also be combined with other compounds to alter its properties, extending its usefullness. Combining it with tin causes it to attached to red blood cells, allowing examination of the heart and blood vessels.

Its short half life of only 6 hours minimises a patients exposure to radiation, making it quite safe to use. In addition, it is not used naturally by any part of the body so it isn't abosrbed, meaning that it can be used to examine radiation sensitive areas such as the heart and kidneys.

Its short half life however also means that it must be produced near where it is used, potentially limiting its usefullness. On balance however, the properties of Technetium 99m make it very useful.

In a test I would probably write that better/more concisely but those are the points I would want to cover...

Now a big marker:
Evaluate the impact of industrial sources of sulfur dioxide and nitrogen oxides on the environment, making use of appropriate chemical equations. (7)

 

[kingkong123]

Re: HSC 2012 Chemistry Marathon

what is the temperature and pressure in which high density polyethylene is made? (confused bcos in excel it says 'just above 300 celsius' whereas in KISS booklet it says at about 60 celsius..which ones correct..can it b a typo

LDPE is conducted in an environment with pressure equivalent to approximately 3000 atmospheres, and with extremely high temperatures. The high pressure atmosphere leads to haphazard branching in the propagation process, leading to the low density. HDPE on the other hand is conducted using the Ziggler-Natta process. Pressure equivalent to only a few atmospheres is required with low temperatures, due to the catalyst present. This low pressure results in a tightly packed, high density polymer.

Right/Wrong?

 

[someth1ng]

Re: HSC 2012 Chemistry Marathon

what is the temperature and pressure in which high density polyethylene is made? (confused bcos in excel it says 'just above 300 celsius' whereas in KISS booklet it says at about 60 celsius..which ones correct..can it b a typo

60C is correct AFAIK.

 

[someth1ng]

Re: HSC 2012 Chemistry Marathon

LDPE is conducted in an environment with pressure equivalent to approximately 3000 atmospheres, and with extremely high temperatures. The high pressure atmosphere leads to haphazard branching in the propagation process, leading to the low density. HDPE on the other hand is conducted using the Ziggler-Natta process. Pressure equivalent to only a few atmospheres is required with low temperatures, due to the catalyst present. This low pressure results in a tightly packed, high density polymer.

Right/Wrong?

Correct, it's "Ziegler-Natta" by the way. Having poor spelling gives the impression that you don't know which you clearly do.

 

[someth1ng]

Re: HSC 2012 Chemistry Marathon

Evaluate the impact of industrial sources of sulfur dioxide and nitrogen oxides on the environment, making use of appropriate chemical equations. (7)

These are what I wrote a couple of days ago:
• Oxides of sulphur and nitrogen are highly acidic and toxic.
• These oxides cause environmental issues such as acid rain and the release of toxic fumes and the levels of these oxides have been rising since the industrial revolution.
• Sulphur oxides: Sulphur Dioxide (SO2) and Sulphur Trioxide (SO3)
• Nitrogen Oxides: General formula of NXOY
• Sulphur oxides react with water to form corrosive acids:
H2O(l) + SO2(g) --> H2SO3 (aq) [Sulphurous Acid]
H2O(l) + SO3(g) --> H2SO4 (aq) [Sulphuric Acid]
• Sulphuric acid is a strong acid with highly corrosive properties and can quickly damage and even destroy flora and fauna in the environment.
• Sulphuric acid can also corrode important monuments and stone buildings and statues, especially if they readily react with acids such as limestone.
• Many Nitrogen Oxides are also highly corrosive, especially Nitric Acid have a potential to pose extreme harm to humans due to its corrosive nature.
• Some Nitrogen oxides form acids in solution and some are toxic gases:
H2O(l) + NO2 (g) --> HNO3(aq)+HNO2(aq) [Nitric Acid and Nitrous Acid]
Dinitrogen Tetroxide: N2O4(g) is a highly toxic gas as it is a powerful oxidiser and inhaling this gas in significant quantities can be fatal.

I think this is a pretty solid answer.

Next question:

Clearly indicate the similarities and differences between the model of acids described by Humphrey Davy and the model developed by Bronsted and Lowry.

 

[nightweaver066]

Re: HSC 2012 Chemistry Marathon

These are what I wrote a couple of days ago:
• Oxides of sulphur and nitrogen are highly acidic and toxic.
• These oxides cause environmental issues such as acid rain and the release of toxic fumes and the levels of these oxides have been rising since the industrial revolution.
• Sulphur oxides: Sulphur Dioxide (SO2) and Sulphur Trioxide (SO3)
• Nitrogen Oxides: General formula of NXOY
• Sulphur oxides react with water to form corrosive acids:
H2O(l) + SO2(g) --> H2SO3 (aq) [Sulphurous Acid]
H2O(l) + SO3(g) --> H2SO4 (aq) [Sulphuric Acid]
• Sulphuric acid is a strong acid with highly corrosive properties and can quickly damage and even destroy flora and fauna in the environment.
• Sulphuric acid can also corrode important monuments and stone buildings and statues, especially if they readily react with acids such as limestone.
• Many Nitrogen Oxides are also highly corrosive, especially Nitric Acid have a potential to pose extreme harm to humans due to its corrosive nature.
• Some Nitrogen oxides form acids in solution and some are toxic gases:
H2O(l) + NO2 (g) --> HNO3(aq)+HNO2(aq) [Nitric Acid and Nitrous Acid]
Dinitrogen Tetroxide: N2O4(g) is a highly toxic gas as it is a powerful oxidiser and inhaling this gas in significant quantities can be fatal.

I think this is a pretty solid answer.

Next question:

You should talk about acid rain.

You should include a chemical equation in the chemical corrosion of limestone buildings.

Your chemical equation for the formation for nitric and nitrous acid is not balanced, it is 2H2O(l).

How can sulphuric acid destroy fauna? Fauna = animals. Perhaps say something about increasing acidity of inland water bodies such that the pH decreases.
Aquatic life cannot sustain themselves at pH < 5, and will eventually die if the pH decreases to that level due to acid rain.

Nitrogen oxides are not harmful to humans due to their corrosive nature, but due to their ability to ionise in to acids if the gases are inhaled. Same applies to sulphur oxides.

 

[study-freak]

Re: HSC 2012 Chemistry Marathon

Identify the standard conditions required to produce a table of reduction potentials based on galvanic cells constructed using a hydrogen electrode.
An electrochemical cell is produced using two half cells. One cell consists of a solution of Fe2+ and Fe3+ with an inert platinum electrode, the other cell consists of a copper electrode in a solution of Cu2+. Write equations for each half cell and calculate the expected standard cell potential.

hydrogen half cell*

I will just dot point this:

- Ethanol is the most used solvent because it has the ability to be a solvent for both polar and non-polar substances.
- The polar hydroxide functional group gives ethanol the ability to be miscible in polar substances.
- The non-polar alkyl part allows ethanol to be miscible in non-polar substances.
- Essentially, having the ability to be miscible in both polar and non-polar substances gives ethanol more effectiveness as a solvent.

Good answer. In a test, hopefully you'll draw a nice structural formula of ethanol showing both the hydroxide functional group and the alkyl chain.

Post a new questions please!

hydroxy or hydroxyl*

LDPE is conducted in an environment with pressure equivalent to approximately 3000 atmospheres, and with extremely high temperatures. The high pressure atmosphere leads to haphazard branching in the propagation process, leading to the low density. HDPE on the other hand is conducted using the Ziggler-Natta process. Pressure equivalent to only a few atmospheres is required with low temperatures, due to the catalyst present. This low pressure results in a tightly packed, high density polymer.

Right/Wrong?

Correct, it's "Ziegler-Natta" by the way. Having poor spelling gives the impression that you don't know which you clearly do.

Having wrong info is even more serious a problem.
Low pressure doesn't account for the high density of the final product. It's the catalysis itself.

 

[someth1ng]

Re: HSC 2012 Chemistry Marathon

You should talk about acid rain.

You should include a chemical equation in the chemical corrosion of limestone buildings.

Your chemical equation for the formation for nitric and nitrous acid is not balanced, it is 2H2O(l).

How can sulphuric acid destroy fauna? Fauna = animals. Perhaps say something about increasing acidity of inland water bodies such that the pH decreases.
Aquatic life cannot sustain themselves at pH < 5, and will eventually die if the pH decreases to that level due to acid rain.

Nitrogen oxides are not harmful to humans due to their corrosive nature, but due to their ability to ionise in to acids if the gases are inhaled. Same applies to sulphur oxides.

• Oxides of sulfur and nitrogen are highly acidic and toxic.
• These oxides cause environmental issues such as acid rain and the release of toxic fumes and the levels of these oxides have been rising since the industrial revolution.
• Sulfuric acid is a strong acid with highly corrosive properties and can quickly damage and even destroy flora and fauna by decreasing the pH of inland water bodies in the environment making the water unsustainable for aquatic life.
• Sulfur oxides: Sulfur Dioxide (SO₂) and Sulfur Trioxide (SO₃)
• Nitrogen oxides: General formula of N_XO_Y
• Sulfur oxides react with water to form corrosive acids:

H₂O_(l) + SO_2(g) H₂SO_{3 (aq)} [Sulfurous Acid]
H₂O_(l) + SO_3(g) H₂SO_{4 (aq)} [Sulfuric Acid]

• Sulfuric acid can also corrode important monuments and stone buildings and statues, especially if they readily react with acids such as limestone.
• H₂SO_4(aq) + CaCO₃ à H₂O_(l) + CO_2(g) + CaSO_4(aq)
• Many nitrogen oxides are also highly corrosive due to their potential to ionise into acids such as nitric acid when inhaled.
• Some nitrogen oxides form acids in solution and some are toxic gases:

H₂O_(l) + 2NO_{2 (g)} HNO_3(aq)+HNO_2(aq) [Nitric Acid and Nitrous Acid]

• Dinitrogen Tetroxide: N₂O_4(g) is a highly toxic gas as it is a powerful oxidiser and inhaling this gas in significant quantities can be fatal.

There, it's now balanced and I think a lot of your points are now covered.

 

[kingkong123]

Re: HSC 2012 Chemistry Marathon

Having wrong info is even more serious a problem.
Low pressure doesn't account for the high density of the final product. It's the catalysis itself.

The Ziegler-Natta catalyst allows surface polymerisation to occur which results in a tightly packed polymer, but the low pressure is definitely a contributing factor as well. If you look at LDPE, the extremely high pressure results in the radicals backbiting and joining haphazardly, resulting in the low density - by the same token, in HDPE, despite the presence of the catalyst, the low pressure allows for a more controlled propagation process where the monomers can join closely together.

 

[study-freak]

Re: HSC 2012 Chemistry Marathon

The Ziegler-Natta catalyst allows surface polymerisation to occur which results in a tightly packed polymer, but the low pressure is definitely a contributing factor as well. If you look at LDPE, the extremely high pressure results in the radicals backbiting and joining haphazardly, resulting in the low density - by the same token, in HDPE, despite the presence of the catalyst, the low pressure allows for a more controlled propagation process where the monomers can join closely together.

The linearity of the final product when the Ziegler-Natta catalyst is used is a result of its reaction mechanism (enabled by the catalyst), rather than pressure or temperature.
Back-biting is characteristic of LDPE radical polymerisation reactions, but this reaction is not that of free radicals.

 

[viraj30]

Re: HSC 2012 Chemistry Marathon

since there are no questions in last posts ill post an easy one!- how much it costs to raise 32 litres of water by 20 degrees if it costs 15cents/kwh...??

 

[someth1ng]

Re: HSC 2012 Chemistry Marathon

since there are no questions in last posts ill post an easy one!- how much it costs to raise 32 litres of water by 20 degrees if it costs 15cents/kwh...??

This is the weirdest question (for Chemistry) that I've seen to date - like, it's not really HSC but LOL