HSC Chemistry Question Thread

[jakesilove]

Yup! I meant other exams before chem. Typo lol

If you have a tonne of exams before Chemistry, definitely focus on those. I would take the bulk of you study time as focussed towards imminent subjects, making sure to give yourself a break wherever possible. However, as Chem gets closer (so maybe after Eng Paper 2) start to filter in a past papers or two. Maybe do a Chem past paper every couple of days, and go over your notes etc. etc. just so you don't lose track. When Chem is about a week away, focus on it must, much more. However, you have to take exams one at a time!

[RuiAce]

Yup! I meant other exams before chem. Typo lol

I think Jake has you all covered.

For someone like me I actually gunned the first few weeks of stuvac on the courses to be examined later, in an attempt to store it in my long term memory. When I went back to it, it worked

[RuiAce]

Hi, I was just wondering if anyone had any word documents or something of the like with heaps of the Chemistry-maths equation questions that we can be given. Thanks

p.s. not a chemical equation list with all of the equations we need to know

I have a small table. I'll upload it later.

It has all of what's needed except %(w/w) stuff.

[Hua Fei]

Hey there!
I think this might be a stupid question but I really don't understand if ozone being a polar molecule has any effect on its boiling point (-111 degrees Celsius) being higher than oxygen's boiling point (-183 degrees Celsius). If the polarity does have an effect, then how and why?

Thank you very much!

[jakesilove]

Hey there!
I think this might be a stupid question but I really don't understand if ozone being a polar molecule has any effect on its boiling point (-111 degrees Celsius) being higher than oxygen's boiling point (-183 degrees Celsius). If the polarity does have an effect, then how and why?

Thank you very much!

Hey!

By my understanding, the main difference in boiling point comes about because of their relative size. Ozone is bigger, and so the boiling point is higher (ie. more energy is required to vapourize larger molecules)!

However, polarity may come into play as well. Polar molecules "stick together" better, as dipole-dipole action is stronger than dispersion forces. So, MORE energy is required to break intermolecular bonds for polar molecules than non-polar molecules! Still, I'd stick with the first explanation

Jake

[Hua Fei]

Hey!

By my understanding, the main difference in boiling point comes about because of their relative size. Ozone is bigger, and so the boiling point is higher (ie. more energy is required to vapourize larger molecules)!

However, polarity may come into play as well. Polar molecules "stick together" better, as dipole-dipole action is stronger than dispersion forces. So, MORE energy is required to break intermolecular bonds for polar molecules than non-polar molecules! Still, I'd stick with the first explanation

Jake

Thank you Jake! I understand it now   =D

[jakesilove]

Thank you Jake! I understand it now   =D

Great! Let me know if you have any other questions!

[Gregs]

I have a small table. I'll upload it later.

It has all of what's needed except %(w/w) stuff.

Thanks Rui

[RuiAce]

Hey there!
I think this might be a stupid question but I really don't understand if ozone being a polar molecule has any effect on its boiling point (-111 degrees Celsius) being higher than oxygen's boiling point (-183 degrees Celsius). If the polarity does have an effect, then how and why?

Thank you very much!

Hey!

By my understanding, the main difference in boiling point comes about because of their relative size. Ozone is bigger, and so the boiling point is higher (ie. more energy is required to vapourize larger molecules)!

However, polarity may come into play as well. Polar molecules "stick together" better, as dipole-dipole action is stronger than dispersion forces. So, MORE energy is required to break intermolecular bonds for polar molecules than non-polar molecules! Still, I'd stick with the first explanation

Jake

I am fairly positive it does. Ozone is polar whereas oxygen is not. Dipole-dipole interactions are stronger as you said there Jake

[Hua Fei]

Hey there!

Question: An experiment was performed where equal volumes of 0.1 mol/L Pb(NO3)2 and 0.1 mol/L KI solutions were mixed. Soon after mixing a precipitate was observed.
Complete the table below to show the concentration of all ions present in solution at each stage of the experiment.

Note: the table & the answers are attached.
What I understand: the first row of answers and how you get from the 2nd row to the third row...don't understand the other parts (i.e. how you get from the 1st to the 2nd row) 

[sweetcheeks]

Hey there!

Question: An experiment was performed where equal volumes of 0.1 mol/L Pb(NO3)2 and 0.1 mol/L KI solutions were mixed. Soon after mixing a precipitate was observed.
Complete the table below to show the concentration of all ions present in solution at each stage of the experiment.

Note: the table & the answers are attached.
What I understand: the first row of answers and how you get from the 2nd row to the third row...don't understand the other parts (i.e. how you get from the 1st to the 2nd row) 

There are equal volumes of the lead (ii) nitrate and potassium iodide solutions. When you add them together, the concentration will be halved, as the volume is doubled. Say you have 100mL of each solution, adding them together will result in a combined volume of 200mL, double the initial volume, resulting in half the original concentration.

[Hua Fei]

There are equal volumes of the lead (ii) nitrate and potassium iodide solutions. When you add them together, the concentration will be halved, as the volume is doubled. Say you have 100mL of each solution, adding them together will result in a combined volume of 200mL, double the initial volume, resulting in half the original concentration.

Oh. My. God. I can't believe I forgot that! - Thank you!!!

[marynguyen18]

Why is ethanol a good source for alternative fuel in terms of boiling point and heat of combustion? 

[jakesilove]

Why is ethanol a good source for alternative fuel in terms of boiling point and heat of combustion?

Well, when we combust Ethanol (make sure you know the equation for this!) it releases a decent amount of energy. It also has a relatively low boiling point, which makes it easier to combust. So, when we burn Ethanol, we can use the energy released to run machines/cars/whatever we feel like!

[marynguyen18]

thank you Jake