Predictions for Chemistry 2014 HSC? (1 Viewer)

[SuchSmallHands]

1) The standard galvanic cell conditions weren't used. Standard conditions involve a inert platinum electrode immersed in 1.0 mol/L HCl with Hydrogen gas bubbled in at 100 kPa and 25 degrees Celsius
2) Low concentrations were being used so there were less cations to gain electrons and travel through the external circuit towards the cathode, thus producing a lower experimental potential difference than the theoretical value
3) Metals not completely pure (were they cleaned with emery paper beforehand) or impurities in electrolyte solutions.

If the third point isn't valid enough, some bs about how low quality voltmeters were used which put load on the external circuit thereby reducing potential voltage and/or the person observing was like close to blind etc

I'd add resistance of the wires to this.

 

[SuchSmallHands]

Hmm okay

Account for ethanol's status as a universal solvent (4 marks)

- polar hydroxyl group
- non-polar ethyl group
- capacity to form hydrogen bonds
- cute diagram of ethanol molecule with all of the above labelled
- 'like dissolves like'

 

[QZP]

... what am I missing?

Some criticism
- You're using a hydrogen electrode? Isn't the question asking for voltage between two metals X and Y?
- 2 is similar to 1 (you could also argue the alternative; too high concentration)

Edit: Also your conditions for standard galvanic cell is wrong

 

[SuchSmallHands]

Some criticism
- You're using a hydrogen electrode? Isn't the question asking for voltage between two metals X and Y?
- 2 is similar to 1 (you could also argue the alternative; too high concentration)

Edit: Also your conditions for standard galvanic cell is wrong

Really? I always thought we used standard ambient temp and pressure for Galvanic cells as well. Are we just supposed to use standard temp and pressure?

 

[faisalabdul16]

Do you really think its nice? idk man that's like a 1/3 to me

My 3 reasons would be:
1) Concentration of ions were not 1mol/L
2) Temperature at which voltage was measured was not 25 degrees celsius
3) Pressure at which voltage was measured was not 100kPA

Also QZP! I think you have to be the one to criticize answers.

 

[Immortality]

My 3 reasons would be:
1) Concentration of ions were not 1mol/L
2) Temperature at which voltage was measured was not 25 degrees celsius
3) Pressure at which voltage was measured was not 100kPA

Also QZP! I think you have to be the one to criticize answers.

You could also add in that the electrode surfaces were not cleaned.

 

[faisalabdul16]

You could also add in that the electrode surfaces were not cleaned.

Yeap

 

[QZP]

Really? I always thought we used standard ambient temp and pressure for Galvanic cells as well. Are we just supposed to use standard temp and pressure?

AH you are right. Sorry guys. I was thinking of standard conditions for the BOD test (its 20deg not 25deg)

25 deg, 100 kPa

 

[QZP]

My 3 reasons would be:
1) Concentration of ions were not 1mol/L
2) Temperature at which voltage was measured was not 25 degrees celsius
3) Pressure at which voltage was measured was not 100kPA

Also QZP! I think you have to be the one to criticize answers.

This is good But maybe I would have put 2 + 3 together i.e. Standard conditions were not used (25 deg C, 100kPa pressure). And then put a third point (like the impurities as mentioned by harrypotterfan)

 

[faisalabdul16]

This is good But maybe I would have put 2 + 3 together i.e. Standard conditions were not used (25 deg C, 100kPa pressure). And then put a third point (like the impurities as mentioned by harrypotterfan)

True true, nonetheless they can be separated however to a marker you'd be showing them you're knowledge through grouping them and mentioning another reason.

New Question:

Define what a condensation polymer is. Provide an example (synthetic example) as well as how it is made. - 3 marks.

 

[QZP]

In a science lab these conditions are applied (hydrogen gas being bubbled through etc regardless of the electrolytes/anode/cathode etc) as a reference. So I dont think I'd lose a mark for saying that...

Yes, electrode surfaces should be cleaned with sand paper/emery paper

Measuring the voltage between two metals doesn't involve H2 gas though... that's why I deducted a mark. What you're thinking of is calculating the electric potential of metals RELATIVE to H2 gas (which forms the electric potential table)

 

[QZP]

Omg idk any synthetic condensation polymers :'( Is this even part of syllabus. We should do 6/7 mark Q's from past papers and analyse where the marks go or critique responses

 

[faisalabdul16]

Omg idk any synthetic condensation polymers :'( Is this even part of syllabus. We should do 6/7 mark Q's from past papers and analyse where the marks go or critique responses

I remember being taught it. Not sure if in syllabus

Condensation polymers are polymers formed by the 'head-to-tail' joining of two monomers which have functional groups at each end and result in the loss of a molecule, usually water. A synthetic example of a condensation polymer is polyesters. PET polymers are formed when terepthalic acid and ethylene glycol condense to produce polyethene terepthalate forms.

Another synthetic example is nylon 6. Nylon 6 is produced from the condensation polymerisation of 6-aminohexanoic acid.

Okay, provide a 6/7 marker question

 

[SuchSmallHands]

True true, nonetheless they can be separated however to a marker you'd be showing them you're knowledge through grouping them and mentioning another reason.

New Question:

Define what a condensation polymer is. Provide an example (synthetic example) as well as how it is made. - 3 marks.

Condensation polymers are those which lose small molecules (usually H2O) as they form. An example of a synthetic condensation polymer is nylon, formed by reacting a diamine and a dicarboxylic acid in a 1:1 ratio (I know this isn't detailed at all, I didn't realise synthetic condensation polymers were on our syllabus?)

 

[SuchSmallHands]

I believe it is. I remember being taught it. Very rarely do you even get asked about it.

Condensation polymers are polymers formed by the 'head-to-tail' joining of two monomers which have functional groups at each end and result in the loss of a molecule, usually water. A synthetic example of a condensation polymer is polyesters. PET polymers are formed when terepthalic acid and ethylene glycol condense to produce polyethene terepthalate forms.

Another synthetic example is nylon 6. Nylon 6 is produced from the condensation polymerisation of 6-aminohexanoic acid.

Okay, provide a 6/7 marker question

Are you sure that's on the syllabus? I only remember doing cellulose for condensation polymerisation? (I'm probably just forgetting though)

 

[faisalabdul16]

Are you sure that's on the syllabus? I only remember doing cellulose for condensation polymerisation? (I'm probably just forgetting though)

I'll check

 

[faisalabdul16]

Sorry guys, not part of syllabus.
My bad.

Syllabus only mentions cellulose, defining what a condensation polymer is.

Does NOT mention synthetic.

 

[SuchSmallHands]

Sorry guys, not part of syllabus.
My bad.

Syllabus only mentions cellulose, defining what a condensation polymer is.

Does NOT mention synthetic.

Thank goodness, I don't think my dodgy nylon answer would go down too well for a three mark question.

 

[faisalabdul16]

Thank goodness, I don't think my dodgy nylon answer would go down too well for a three mark question.

hahaha my bad sorry.

Evaluate the importance of monitoring and managing the conditions used in the Haber process. - 7 marks

Pretty decent question, but marking criteria i would assume wants top-notch detail lol

 

[SuchSmallHands]

hahaha my bad sorry.

Evaluate the importance of monitoring and managing the conditions used in the Haber process. - 7 marks

Pretty decent question, but marking criteria i would assume wants top-notch detail lol

I'd expect 3-4 marks for that, they must want ridiculous detail (which I won't be giving since this isn't my actual HSC)

Marked fluctuations in the conditions under which the Haber Process takes place (450-500 degrees Celsius and 200 atmospheres pressure) is not favourable for the following reasons:

TEMPERATURE
- decrease: causes the reaction to proceed more slowly, thus renders the process less economically viable
- increase: the reaction N2 + 3H2 ----> 2NH3 is exothermic. Therefore, as temperature is increased the position of the equilibrium shifts more to the left to minimise the disturbance in accordance with Le Chatelier's Principle, thus reforming reactants instead of creating more product (ammonia). As the goal of the Haber process is to synthesise ammonia, this is not desirable

PRESSURE
- decrease: the Haber Process involves four moles of reactants combining to form two moles of products. Thus, high pressure favours the formation of products (ammonia) in order to relieve this pressure. Thus, decreasing pressure leads to a decrease in ammonia yield, which is not desirable.
- increase: sustaining a very high pressure is cost intensive, thus a marked increase in temperature can cause the process to become economically inefficient, as production cost may exceed the cost of the product to the market.

Thus it is highly important to ensure these conditions are strictly monitored in order to promote financial efficiency and high ammonia yield.