HSC Chemistry Question Thread

[jakesilove]

Thanks for your help! I do have a couple more questions though:
1. if the titrate is in the burette, what do you call the solution in the flask...is it always just standard solution?
2. do soaps form miscelles only when they are around particles are are the always in miscelles even when not surrounding grease...if that makes sense?
3. What is chain stiffening and what is it's effect?
4. Do you need to know the name and structure of a fat or oil like glycerol tristreate for saponification?
Thanks!

1. We call it the titrant, and the titre

2. No idea, hopefully someone who does industrial can help

3. Nope.

4. Nope

RUI!

[anotherworld2b]

Thank you for your help anyway 
I also wondering for hydrocarbons how do make sure you draw a isomer and not a completely different compound?
I sometimes accidently draw a entirely different compound instead of a isomer

[jakesilove]

Two identical ships are sunk in seawater. One is sunk in shallow water (60 m)
and the other in deep water (4000 m). Explain how the rusting processes differ
in these two ships. Include equations in your answer.  (7m)

Need some help with this, could somebody write a proper response to it?

Not going to be able to give you a full response, but here are some things to discuss

Shallow waters

Increased oxygen, increased temperature, but decreased pressure. Rusting will occur as usual, by the usual equations, which you write out etc. etc. Nothing fancy here

Deep waters

Decreased oxygen, decreased temperature, but increased pressure. Rusting would be accelerated if not for the lack of Oxygen and cold temperatures, which should decrease the rate of corrosion. However, several factors increase the rate

Sulfate-reducing bacteria forces iron to oxidise (as something has to, for sulfate to reduce). Sulfate is leeched from volcanic rock etc. This leads to increased rusting

Acidic microenvironments due to areas of the ship etc. result in an 'easier' pathway for rust; check the voltage required for an H+ and Iron cell, and it will be less than an H2O/O2 and Iron cell, making it an easier process.


Hope that outline helps! Include loads of equations as well

[jakesilove]

Thank you for your help anyway 
I also wondering for hydrocarbons how do make sure you draw a isomer and not a completely different compound?
I sometimes accidently draw a entirely different compound instead of a isomer

Not sure how to help you here; just make sure you have the same number of elements. Potentially draw yourself a hint section, where you write how many Carbons, Hydrogens etc. you have. When you draw out an isomer, check that you still have the same number of each element!

[kimmie]

How does the concentration of electrolyte and nature of electrolyte affect electrolysis? Like aren't they both the same thing?

[Ayyddaan]

Not going to be able to give you a full response, but here are some things to discuss

Shallow waters

Increased oxygen, increased temperature, but decreased pressure. Rusting will occur as usual, by the usual equations, which you write out etc. etc. Nothing fancy here

Deep waters

Decreased oxygen, decreased temperature, but increased pressure. Rusting would be accelerated if not for the lack of Oxygen and cold temperatures, which should decrease the rate of corrosion. However, several factors increase the rate

Sulfate-reducing bacteria forces iron to oxidise (as something has to, for sulfate to reduce). Sulfate is leeched from volcanic rock etc. This leads to increased rusting

Acidic microenvironments due to areas of the ship etc. result in an 'easier' pathway for rust; check the voltage required for an H+ and Iron cell, and it will be less than an H2O/O2 and Iron cell, making it an easier process.


Hope that outline helps! Include loads of equations as well

That's perfect! Thanks heaps! Are there any specific equations that you think should be listed?

[jakesilove]

How does the concentration of electrolyte and nature of electrolyte affect electrolysis? Like aren't they both the same thing?

Not QUITE the same thing; nature of electrolyte could be like what the electrolyte is actually made up of (Silver Nitrate, Potassium Nitrate etc.) whereas concentration is... concentration. More concentrated = better electrolyte, nature of electrolyte must be soluble etc.

[jakesilove]

That's perfect! Thanks heaps! Are there any specific equations that you think should be listed?

Yep! You should have them in your notes somewhere, just be able to go from Water + Oxygen + Iron all the way to rust (I remember there being a couple steps), and then personally I would just write out the equations on the table of standard potentials regarding sulfate and Hydrogen ions

[nimasha.w]

hey! how would you work this one out

[RuiAce]

3. Nope.

4. Nope

RUI!

YES SIR!

Thanks for your help! I do have a couple more questions though:
1. if the titrate is in the burette, what do you call the solution in the flask...is it always just standard solution?
2. do soaps form miscelles only when they are around particles are are the always in miscelles even when not surrounding grease...if that makes sense?
3. What is chain stiffening and what is it's effect?
4. Do you need to know the name and structure of a fat or oil like glycerol tristreate for saponification?
Thanks!

3. I haven't seen this term before. What context are we talking about?

4. You do need to know the name of one but I believe you're allowed off with the structure.

[jakesilove]

hey! how would you work this one out

Hey! If you look to the table of standard potentials, you'll realise that for the best cell, we want something very high on the list, and something very low on the list. What does that means? Something very reactive, and something very unreactive! Clearly, Q is the most reactive, and R is the least reactive, so we'll use those. Thus, the answer is C

[kimmie]

How do impressed current systems provide cathodic protection?

[Sssssrr]

can someone please explain how to use significant figures in chemistry? thanks

[Furrrball]

Thanks for your help! I do have a couple more questions though:
1. if the titrate is in the burette, what do you call the solution in the flask...is it always just standard solution?
2. do soaps form miscelles only when they are around particles are are the always in miscelles even when not surrounding grease...if that makes sense?
3. What is chain stiffening and what is it's effect?
4. Do you need to know the name and structure of a fat or oil like glycerol tristreate for saponification?
Thanks!

For Q3. The soap molecules form a micelle when they carry out their job as an emulsifier for the water & grease.  So only when the grease is present.
The hydrocarbon-tail of the soap forms dispersion forces with the grease and the anionic head forms  ion-dipole interactions with the water molecule.

Hope that answers your question.

[jakesilove]

How do impressed current systems provide cathodic protection?

This one is pretty straight forward; the problem is that Iron has oxidised (lost electrons) right? So, we can pass a current along it (current = moving electrons) to reduce it again (gain electrons)!

Simple as that