HSC Chemistry Question Thread

[Natasha.97]

Would appreciate help with the following Qs:
14. https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/20270053_1279294878862699_251626619_n.png?oh=0833834537ad91acfa67f1eec4e6a948&oe=59763A9F
The answer is D and I understand, but can someone explain why it is not C?
Shipwrecks Q:
https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/20270053_1279294878862699_251626619_n.png?oh=0833834537ad91acfa67f1eec4e6a948&oe=59763A9F
The sample answer in the booklet was literally 2 pages and far too detailed for 6 marks. What would this Q require for the 6?

Hi!

For AAS, the sample being shone through the sample is usually already known so we know which wavelengths are absorbed. AAS is used to determine the concentrations, so it should be measuring the intensity of light absorbed.

Hope this helps

[bsdfjnlkasn]

Hey there!

Was just wondering what were the most common covalent bond molecules that we are asked to draw in exams - sorry if that seems really random, just want to know what to expect

Thank you

[MisterNeo]

Hey there!

Was just wondering what were the most common covalent bond molecules that we are asked to draw in exams - sorry if that seems really random, just want to know what to expect

Thank you

I know that in Production of Materials, 99.99% of the time they will ask you to draw ethanol and glucose/cellulose polymerisation.
In Chemical Monitoring, they will definitely ask you to draw oxygen and ozone (you must draw coordinate covalents using an arrow).
In Acidic Enviro, they might ask you to draw ionisation of strong vs weak acid, or an ester.

[kiwiberry]

Hey there!

Was just wondering what were the most common covalent bond molecules that we are asked to draw in exams - sorry if that seems really random, just want to know what to expect

Thank you

Also citric acid! Make sure you remember its super long name and know how to draw it haha, that came up in my half yearly. If you do industrial, you need to know how to draw the saponification reactions as well as the structure of all the different types of detergents

[Annie657]

So at my school we do chem of art :/ And I was wondering how to explain what a hydrated ion in solution is? Like does it have to be an ionic molecule that disassociates in water or can they be covalent? My sheet says AlCl₃ is covalent but I'm not sure why.

Thankyou!

[Natasha.97]

So at my school we do chem of art :/ And I was wondering how to explain what a hydrated ion in solution is? Like does it have to be an ionic molecule that disassociates in water or can they be covalent? My sheet says AlCl₃ is covalent but I'm not sure why.

Thankyou!

Hi!

I don't do that option, but found some stuff online:

Definitions:
- Hydrated ions: Transition metals in solution that form hydrated ions as the polar water atoms surround the metal cations
- Ligands: Anions/polar molecules attached to a metal cation by coordinate bonding (one atom donates both electrons, also known as a dative covalent bond), using available empty orbitals in the metal ion

Explanation of hydrated ion:
- Water molecule is polar (2 lone pairs on O), resulting in the O side of the H₂O molecule partially negative, and the H₂ side partially positive
- Partially negative side of H₂O molecule is attracted to the anhydrous (without water) cation in solution

Explanation of AlCl₃:
From the above, I agree that it is covalent: Al is the transition metal in solution, and the Cl ions should be the ligands that attach to Al

Hope this helps!

Edited explanation of hydrated ion

[Annie657]

Hi!

I don't do that option, but found some stuff online:

Definitions:
- Hydrated ions: Transition metals in solution that form hydrated ions as the polar water atoms surround the metal cations
- Ligands: Anions/polar molecules attached to a metal cation by coordinate bonding (one atom donates both electrons, also known as a dative covalent bond), using available empty orbitals in the metal ion



Explanation of hydrated ion:
- Water molecule is polar (2 lone pairs on O₂), resulting in the O₂ side of the H₂O molecule partially negative, and the H₂O side partially positive
- Partially negative side of H₂O molecule is attracted to the anhydrous (without water) cation in solution

Explanation of AlCl₃:
From the above, I agree that it is covalent: Al is the transition metal in solution, and the Cl ions should be the ligands that attach to Al

Hope this helps!

Thankyou so much for all that research! Most of it makes sense now, except isn't a covalent bond between a non metal and non metal atom? Sorry this is what I remember from junior science :/

[Natasha.97]

Thankyou so much for all that research! Most of it makes sense now, except isn't a covalent bond between a non metal and non metal atom? Sorry this is what I remember from junior science :/

Hi Annie!

Yes, a covalent bond is usually between 2 non-metal atoms. Hopefully someone else can answer why AlCl₃ is covalent, as I'm not completely sure

[anotherworld2b]

I was wondering when naming organics would you name bromo before ethy;?

[Daniyahasan]

I was wondering when naming organics would you name bromo before ethy;?

check this out; maybe itll help you
http://www.chemguide.co.uk/basicorg/conventions/names.html

[bluecookie]

Hey guys, you somehow missed my question a few posts ago >.< XD (I think it got buried under the mountain of questions lol)

Degree of ionisation = [H+]/[Acid] x (amount of mol)/(amount of h ions) x the whole thing by 100%. How do we find the hydrogen concentration and amount of h ions?

[Bubbly_bluey]

Hey guys, you somehow missed my question a few posts ago >.< XD (I think it got buried under the mountain of questions lol)

Degree of ionisation = [H+]/[Acid] x (amount of mol)/(amount of h ions) x the whole thing by 100%. How do we find the hydrogen concentration and amount of h ions?

Hey! I don't think I'll be much help but do you have the question so I can have a look. From what i understad degree of ionisation is the calulation of the hydronium ions conc/ acid conc as you expressed above. If you want to find hydronium conc and given degree ionisation and acid conc you can work that out by rearranging the formula:
acid conc x degree ionisation = hydronium conc
By the amount of h ions do you mean the number of moles?
If so you can use concentration found above so you can multiply by given volume using : n=CxV
Of course I'm not sure if this is even what you are asking. Just let me know if i even answered your question. Sorry

[MisterNeo]

Hey guys, you somehow missed my question a few posts ago >.< XD (I think it got buried under the mountain of questions lol)

Degree of ionisation = [H+]/[Acid] x (amount of mol)/(amount of h ions) x the whole thing by 100%. How do we find the hydrogen concentration and amount of h ions?

Do you have a question for this?
I'm pretty sure this area of weak acids aren't covered in the Acidic Environment module as we stick to calculating H+ in strong acids using that 10^-pH formula.
 

[anotherworld2b]

thank you

check this out; maybe itll help you
http://www.chemguide.co.uk/basicorg/conventions/names.html

[Bubbly_bluey]

Hi! I'm having trouble with this question. What does it mean by half cell?
The second question can someone explain why the answer can't be B?
Thanks