Suggested Answers - Illuminati

[thushan]

ATARNotes Official Solutions to VCAA 2012 Unit 4 Chemistry Examination

My solutions are up

[rebeccab26]

For 7D could you say that fuel cells require a continuous supply of reactants and removal of produces whereas electrolytic do not?

[Tonychet2]

For 7D could you say that fuel cells require a continuous supply of reactants and removal of produces whereas electrolytic do not?

i wrote that too im getting worried now...

[thushan]

Would pay that actually. The question didn't make clear whether they were talking about that particular electrolysis cells or electrolysis cells in general.

[thushan]

  b) The value in the databook refers to the reaction of methanol in which the co-efficient in front of methanol is 1. There is 2 in the equation in part a.ii. and hence the value is approximately twice as large.

I'm not sure about this one. It specifies the value for delta H calculated using the enthalpy of combustion, and given that we had to multiply it by 2 to get the mark for the previous answer I think this was already assumed. If this is right I think that question's a bit silly.

What if we wrote that they were different because the experiment we used might not have occurred at SLC, or the methanol sample was impure?

Damn stupid mistakes on the midyear ):

isnt the answer because some heat energy is lost from poor insulation? therefore the temperature increases less and the calculated delta H value of methanol is lower

I didn't like the wording of this question. I reckon they should have added an extra part saying "Calculate the delta H value based on the value in your data book," then led with that qn.

[kmp34]

Well according to Illuminati would have  lost 8 marks.
What score would I be likely to get since I got a B+ on they mid years, pretty high sac marks, and go to a competitive school?

[illuminati]

Would they give C for 15?

And why is 20 B not D??

no and
its B because its still produces carbon if you're using hydrocarbons as a fuel

[kimk2kr]

For 5bi and ii(sulfuric acid) i wroyr thermal pollution due to heat being released into the atmosphere and (ii) i wrote excess heat can be used to generate electricity which can be used to run the plant

Is that fine?
 

[illuminati]

For 5bi and ii(sulfuric acid) i wroyr thermal pollution due to heat being released into the atmosphere and (ii) i wrote excess heat can be used to generate electricity which can be used to run the plant

Is that fine?
 

not sure if thermal pollution is a thing.
but if it is should be fine.

[thushan]

That's fine. Thermal pollution is where warm water is released into lakes, rivers and that, increasing the temperature of the water there, decreasing the solubility of O2, killing the fish.

[Nobby]

For 5bi and ii(sulfuric acid) i wroyr thermal pollution due to heat being released into the atmosphere and (ii) i wrote excess heat can be used to generate electricity which can be used to run the plant

Is that fine?

I think you'd definitely get the mark if you specified that the thermal pollution was in regards to water, not sure about atmosphere. I think the second bit is fine.

edit: thushan beat me to it

[charmanderp]

  b) The value in the databook refers to the reaction of methanol in which the co-efficient in front of methanol is 1. There is 2 in the equation in part a.ii. and hence the value is approximately twice as large.

I'm not sure about this one. It specifies the value for delta H calculated using the enthalpy of combustion, and given that we had to multiply it by 2 to get the mark for the previous answer I think this was already assumed. If this is right I think that question's a bit silly.

What if we wrote that they were different because the experiment we used might not have occurred at SLC, or the methanol sample was impure?

Damn stupid mistakes on the midyear ):

isnt the answer because some heat energy is lost from poor insulation? therefore the temperature increases less and the calculated delta H value of methanol is lower

I didn't like the wording of this question. I reckon they should have added an extra part saying "Calculate the delta H value based on the value in your data book," then led with that qn.

Yeah I agree, very dodgy. Considered both possible interpretations before answering and went with what seems like the unpopular choice...

[joseph95]

And why is 20 B not D??

no and
its B because its still produces carbon if you're using hydrocarbons as a fuel

I did the same as you illuminati, but you just contradicted the question. It says which is not a feature of a modern fuel cell, so according to your explanation here they do not have that potential to reduce carbon dioxide emissions, so the answer could be B.
But they do have that potential to because water is usually only produced. So the answer is B.

[bubblefighter]

3b ii: Is using charge of -2 acceptable?

[joseph95]

Yeah I agree, very dodgy. Considered both possible interpretations before answering and went with what seems like the unpopular choice...

I did the same as you because I also thought it was too obvious
Otherwise it was an unbelievably stupid question.