Predictions for Chemistry 2014 HSC? (6 Viewers)

[Beterban]

can you give me a definition for each of these and a method to measure them
my notes are a bit dodgy

 concentrations of common ions:
 total dissolved solids:
 hardness:
 turbidity:
 acidity:
 dissolved oxygen and biochemical oxygen demand

ignored.....

 

[enigma_1]

http://en.wikipedia.org/wiki/William_Lawrence_Bragg

he's been dead for a while

omg lol

 

[enigma_1]

ignored.....

OMG SOORRRRY I don't think we saw this. Let's all do some: I'll do Hardness, DO, BOD.

 

[Queenroot]

at least you have a science department

We pretty much don't because the head teacher is usually the relieving principal cos our principal has issues of leaving all the time. And all the young ones are knocked up.

ahahah ikr

OMGGGG SERIOUSSSSSS???????? How did you find out?????

Someone posted it in our internal group on fb. It wasn't long ago, they're having his funeral soon. That's why he left, it all makes sense now.

Sorry for derail gaiz

 

[seventhroot]

ignored.....

dat seenzone tho

 

[seventhroot]

We pretty much don't because the head teacher is usually the relieving principal cos our principal has issues of leaving all the time. And all the young ones are knocked up.

Someone posted it in our internal group on fb. It wasn't long ago, they're having his funeral soon. That's why he left, it all makes sense now.

Sorry for derail gaiz

really? he didn't continue teaching after he died?

 

[Queenroot]

really? he didn't continue teaching after he died?

r u stupid, he left the school 2 years ago saying it was his "last day" suddenly and his class was like wat
he died only now

 

[SuchSmallHands]

dat seenzone tho

No one has answered the question I put up either :'(

 

[zhertec]

Cracking is the process by which longer chain alkanes can be decomposed into smaller chain alkanes and alkenes in order to align relative production with relative demand. In catalytic cracking, aluminosilicate zeolite catalysts are used in order to decompose hydrocarbon chains at 500oC in the absence of oxygen. In thermal cracking, temperatures of 700-1000oC are used to decompose the chains as they pass through heated metal at 7,000 kPa pressure.

Sorry, I know this isn't enough for four, but I answered this properly before and I'm lazy.

Assess the potential of Ethene as a raw material in industry (five marks)

Another one of these "broad" questions, hate them as it is hard to guess the marking criteria for them.

Ethene is an alkene mainly obtain from the cracking of petrochemicals in which it can undergo different chemical reactions to create products for different applications.

Ethene can undergo radical polymerisation in order to form Low density polyethylene or high density polyethylene depend on the conditions of the the reaction (high pressure and temperature resulting in low density polyethylene due to the backbiting of chains which result in branched chains being formed, having a lower density due to the shape of the chains which decreases the packing of chains, hence used for applications such as cling wrap and plastic bags. Low pressure and temperature can result in linear chains producing a crystalline polymer with higher tension strength and boiling points, allowing it to be used for applications such as bottlecaps and containers). By reacting ethene with other chemicals such as halogens e.g. chlorine, polymers with different properties can be made, all fitting a number of specific applications.

Ethene can also be hydrate to form ethanol, which due to its polar (hydroxyl group) and non-polar (ethyl group) components, it is often used as an industrial solvent as it can dissolve both polar and no polar substances. Ethanol can also be used in automobiles, where certain blends of ethanol with octane will enable the fuel to retain its high octane rating, however with more "cleaner" products being produced due to complete combustion of the short chain (CO2 and Water).

Ethene is also a renewable raw material, through the anaerobic fermentation of glucose, which produces ethanol. The ethanol produced can be dehydrated with a concentrated acidic catalyst to form ethene. However the production of ethene through fermentation is both expensive and results in overall a higher amount of resources used as the fermentation vats need to be kept in specific conditions and the crops that are used to produce ethene need to be high in carbohydrate (sugarcane), requiring a large amount of fertile soil : sacrificing land for other vital crops and in certain areas such as Australia, the arid conditions prevent an economic yield of ethanol to be produced.

Overall ethene is an excellent raw material as its versatility allows it to react with other chemicals to form a wide arrange of products for different applications, however the current production of ethene is detrimental to the environment as large hydrocarbon chains need to be cracked at high temperatures to form ethene, resulting in thermal and atmospheric pollution by the gasses released.

Shove some equations there yada yada.

 

[seventhroot]

r u stupid, he left the school 2 years ago saying it was his "last day" suddenly and his class was like wat
he died only now

my bad

 

[seventhroot]

No one has answered the question I put up either :'(

gg

might as well go look for your calculator

 

[faisalabdul16]

Two questions -

Is copper blue or copper ions?

When you have a galvanic cell with copper as the cathode, why does blue colour fade? (Explain using LCP)

 

[SuchSmallHands]

Two questions -

Is copper blue or copper ions?

When you have a galvanic cell with copper as the cathode, why does blue colour fade? (Explain using LCP)

Ions, copper is that pinky/bronze (I know bronze is a bad word here but I don't know how else to describe it) colour.

 

[faisalabdul16]

Ions, copper is that pinky/bronze (I know bronze is a bad word here but I don't know how else to describe it) colour.

So why does blue colour fade in a galvanic cell with copper as cathode?

 

[Queenroot]

Ions, copper is that pinky/bronze (I know bronze is a bad word here but I don't know how else to describe it) colour.

"Coppery colour" LOL
But yeah ions are blue

 

[SuchSmallHands]

So why does blue colour fade in a galvanic cell with copper as cathode?

Oops missed the second question. As more copper ions are reduced to elemental copper the blue ions are removed from solution, thus reducing the intensity of the blue colouring. Is this a HSCquestion? Because I don't know what to say about LCP that would add to that answer...

 

[Queenroot]

So why does blue colour fade in a galvanic cell with copper as cathode?

Reduced to metal = sea of electrons
Absorbancy of wavelengths change, ta dah coppery colour

 

[zhertec]

Two questions -

Is copper blue or copper ions?

When you have a galvanic cell with copper as the cathode, why does blue colour fade? (Explain using LCP)

Copper metal is pink I believe and the ions are blue.

Q2. In a galvanic cell where copper is the cathode, the blue colour solution of the copper sulfate fades slowly due to the copper ions being reduced to become copper metal. When the copper cathode has an excess of electrons, produced by the oxidation of the anode, it attracts copper Cu2+ ions in which they are reduced to become copper metal, as the concentration of copper ions decrease, the cathode solution becomes more negative, hence to maintain electric neutrality, cations from the salt bridge migrate to the cathode solution.

In terms of LCP um...lol do they ever relate galvanics to lcp? xD

 

[SuchSmallHands]

Assess the potential of Ethene as a raw material in industry (five marks)

Back to this...

 

[faisalabdul16]

Oops missed the second question. As more copper ions are reduced to elemental copper the blue ions are removed from solution, thus reducing the intensity of the blue colouring. Is this a HSCquestion? Because I don't know what to say about LCP that would add to that answer...

You know how the half-cells are equilibrium reactions?

<img src="http://latex.codecogs.com/gif.latex?Cu^{2&plus;}&plus;2e^{-}\rightleftharpoons&space;Cu" title="Cu^{2+}+2e^{-}\rightleftharpoons Cu" />