HSC Chemistry Question Thread

[jakesilove]

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

Hey! Just look for the least number of sig figs in the question. Eg.

13mol/L

41 degrees

1g

Whilst the first two measurements have 2 sig figs, the third only has one, so your answer needs to have one sig fig!

[RuiAce]

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.

Actually I'm still a bit confused (because I don't have resources with me right now). Is this what they mean by 'chain stiffening' because I genuinely don't recall this term being coined

Plus it doesn't seem as though some 'stiffening' is going on

[jakesilove]

Actually I'm still a bit confused (because I don't have resources with me right now). Is this what they mean by 'chain stiffening' because I genuinely don't recall this term being coined

Plus it doesn't seem as though some 'stiffening' is going on

Industrial is a weird option

[RuiAce]

Industrial is a weird option

Lol get any unnecessary thoughts out of your head Jake haha

[Ayyddaan]

Iron corrodes differently under acidic and neutral conditions.
(i) Write an equation to represent the process of rusting under neutral
conditions.

The sample answer was really weird and I don't think it was right. Please help!

[jakesilove]

Iron corrodes differently under acidic and neutral conditions.
(i) Write an equation to represent the process of rusting under neutral
conditions.

The sample answer was really weird and I don't think it was right. Please help!

Something that looks like this would be ideal

[g98]

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

Chain stiffening is used to describe properties of polymers like polyethylene and polystyrene - I think it has something to do with side groups maybe...

[massive]

guys when do you put equilibrium arrows for all that conjugate acid and base stuff? that still confuses me

[Ayyddaan]

(Image removed from quote.)

Something that looks like this would be ideal

What is the 'x' infront of H₂O

[RuiAce]

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

Chain stiffening is used to describe properties of polymers like polyethylene and polystyrene - I think it has something to do with side groups maybe...

I DEFINITELY did not see that get mentioned in PoM.

guys when do you put equilibrium arrows for all that conjugate acid and base stuff? that still confuses me

Well analyse it.

If both substances are weak, then they're not fully ionised, so you have an equilibrium arrow.

If at least one thing is strong, that's going to drive the equation to completion, so you have a one-way arrow

[jakesilove]

What is the 'x' infront of H₂O

It's just kind of a balancing factor; there could be any number of H2O molecules contained within the chemical structure of rust, such that the left hand side balances out with the right hand side.

[anotherworld2b]

I have a quick question is benzene a aromatic?

[Rd2487]

If we are asked to write an equation for incomplete combustion. Which one doe we write the one where CO and CO2 are formed or the one in which C and CO are formed. Or does it not matter?

[tennis1]

When writing buffer equations, do you always make the acid react with H2O to form H3O+ ions and conj base
or do you react it with H3O+?

[jakesilove]

If we are asked to write an equation for incomplete combustion. Which one doe we write the one where CO and CO2 are formed or the one in which C and CO are formed. Or does it not matter?

Doesn't matter! As long as some C or CO is formed, and the equation is balanced