Login

Welcome, Guest. Please login or register.

March 30, 2024, 01:17:12 am

Author Topic: Rod's Chemistry 3/4 Questions Thread  (Read 25680 times)  Share 

0 Members and 1 Guest are viewing this topic.

Rod

  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1755
  • The harder the battle, the sweeter the victory
  • Respect: +101
Rod's Chemistry 3/4 Questions Thread
« on: December 20, 2013, 10:36:06 am »
0
Hi guys,

I just wanted to know how difficult chromatography (chapter 6), spectroscopy (chapter 7) and combining and choosing analytical techniques (chapter 8) are on a scale of 1 to 10. I'll be starting these topics in about one week's time. Obviously, as you can see I'm going ahead, and I just wanted to know whether I should do the review questions. A lot of smart people are telling me I should, while others have told me I shouldn't. I personally like doing questions, as it solidifies my knowledge, but these questions are taking a lot of my study time away.

Thanks

2013-2014:| VCE
2015-2018:| Bachelor of Science (Neuroscience) @ UoM
2019-X:| Doctor of Dental Surgery (discontinued)
2019 -2021:| Master of Physiotherapy

Currently: Physiotherapist working at a musculoskeletal clinic. Back pain, sore neck, headaches or any other pain limiting your study? Give me a PM (although please do see your personal health professional first!)

Any questions related to pathways towards studying dentistry or physiotherapy? Gimmi a PM!

mackintosh

  • Victorian
  • Trailblazer
  • *
  • Posts: 28
  • Respect: 0
  • School Grad Year: 2013
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #1 on: December 20, 2013, 11:18:03 am »
+1
I think that learning the theory of chromatography and spectroscopy techniques  is mainly just memory work- consult both textbooks, others' notes etc. So in that sense it is not too bad. What people find difficult is the interpretation of chromatograms, and readouts from the various instruments- which is what is generally given more marks on the exam. So, in order to maximize your marks on the application side of these topics, I would suggest doing selected review questions (some of them are badly written and not likely to appear on an exam) in conjunction with Checkpoints, Neap or Lisachem books that give you really good targeted practice. Personally I found holidays the best time to cover the most content, and leave more application practice to during the term. Hope this helps

Yacoubb

  • Guest
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #2 on: December 20, 2013, 11:24:14 am »
+1
Hi guys,

I just wanted to know how difficult chromatography (chapter 6), spectroscopy (chapter 7) and combining and choosing analytical techniques (chapter 8) are on a scale of 1 to 10. I'll be starting these topics in about one week's time. Obviously, as you can see I'm going ahead, and I just wanted to know whether I should do the review questions. A lot of smart people are telling me I should, while others have told me I shouldn't. I personally like doing questions, as it solidifies my knowledge, but these questions are taking a lot of my study time away.

Thanks

Chapters 1-4 are really all covered in year 11, so if you had a strong year 11 foundation in volumetric & gravimetric analysis, as well as stoichiometry, then it shouldn't be too difficult.

Rod

  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1755
  • The harder the battle, the sweeter the victory
  • Respect: +101
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #3 on: December 20, 2013, 12:07:09 pm »
0
I think that learning the theory of chromatography and spectroscopy techniques  is mainly just memory work- consult both textbooks, others' notes etc. So in that sense it is not too bad. What people find difficult is the interpretation of chromatograms, and readouts from the various instruments- which is what is generally given more marks on the exam. So, in order to maximize your marks on the application side of these topics, I would suggest doing selected review questions (some of them are badly written and not likely to appear on an exam) in conjunction with Checkpoints, Neap or Lisachem books that give you really good targeted practice. Personally I found holidays the best time to cover the most content, and leave more application practice to during the term. Hope this helps

So are these three chapters mainly memory and interpretations ? And not many calculations?

Thanks
2013-2014:| VCE
2015-2018:| Bachelor of Science (Neuroscience) @ UoM
2019-X:| Doctor of Dental Surgery (discontinued)
2019 -2021:| Master of Physiotherapy

Currently: Physiotherapist working at a musculoskeletal clinic. Back pain, sore neck, headaches or any other pain limiting your study? Give me a PM (although please do see your personal health professional first!)

Any questions related to pathways towards studying dentistry or physiotherapy? Gimmi a PM!

mackintosh

  • Victorian
  • Trailblazer
  • *
  • Posts: 28
  • Respect: 0
  • School Grad Year: 2013
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #4 on: December 20, 2013, 12:24:27 pm »
+1
So are these three chapters mainly memory and interpretations ? And not many calculations?

Thanks
Yeah predominantly. That said,UV-vis calibration curves for example, are often used as a part of a larger stoichiometry question. This often happens in chem (combination of several topics into one question), which is why review questions aren't always the best, as they are not always exam-style. Most people find interpretation the hardest because , eg. in HNMR, it requires logic and referring to the data book , which is definitely higher-level thinking. 

Rod

  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1755
  • The harder the battle, the sweeter the victory
  • Respect: +101
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #5 on: December 20, 2013, 01:34:30 pm »
0
Thanks guys;

Can someone also please help me with gravimetric analysis. Last week I did all the gravimetric analysis questions, but not in the best of ways (kept making mistakes). So I did some more questions today to make up, and had a bit of trouble. My method of answering these questions are;

- Read the question carefully, find the precipitate, write down a fully balanced equation
- After writing down the equation, write down everything you have
- Use mole ratios to convert whatever you have to what you need

Is that method alright? I don't know why but I'm getting heaps of grav-questions wrong. Any help/tips appreciated!
2013-2014:| VCE
2015-2018:| Bachelor of Science (Neuroscience) @ UoM
2019-X:| Doctor of Dental Surgery (discontinued)
2019 -2021:| Master of Physiotherapy

Currently: Physiotherapist working at a musculoskeletal clinic. Back pain, sore neck, headaches or any other pain limiting your study? Give me a PM (although please do see your personal health professional first!)

Any questions related to pathways towards studying dentistry or physiotherapy? Gimmi a PM!

Yacoubb

  • Guest
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #6 on: December 20, 2013, 01:49:37 pm »
+1
Thanks guys;

Can someone also please help me with gravimetric analysis. Last week I did all the gravimetric analysis questions, but not in the best of ways (kept making mistakes). So I did some more questions today to make up, and had a bit of trouble. My method of answering these questions are;

- Read the question carefully, find the precipitate, write down a fully balanced equation
- After writing down the equation, write down everything you have
- Use mole ratios to convert whatever you have to what you need

Is that method alright? I don't know why but I'm getting heaps of grav-questions wrong. Any help/tips appreciated!

When doing gravimetric analysis, there are a number of different analyses covered. For instance, you can determine water content, find the composition of a compound or find the mass of a particular substance by forming a precipitate. The methods I approach for gravimetric analysis:

1. Read the question.
2. Write out the equation; balanced, with states.
3. Apply any given data to my equation (e.g. we might be told that after a silver chloride precipitate is formed, dried and weighed, a mass of 0.754g is obtained. So, over the AgCl(s) on my equation, I'll just take note of the fact that I have that much of it.
4. Use stoichiometry to answer relevant questions.


Rod

  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1755
  • The harder the battle, the sweeter the victory
  • Respect: +101
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #7 on: December 20, 2013, 01:58:05 pm »
0
When doing gravimetric analysis, there are a number of different analyses covered. For instance, you can determine water content, find the composition of a compound or find the mass of a particular substance by forming a precipitate. The methods I approach for gravimetric analysis:

1. Read the question.
2. Write out the equation; balanced, with states.
3. Apply any given data to my equation (e.g. we might be told that after a silver chloride precipitate is formed, dried and weighed, a mass of 0.754g is obtained. So, over the AgCl(s) on my equation, I'll just take note of the fact that I have that much of it.
4. Use stoichiometry to answer relevant questions.

I see, that's a great method. Thanks Yacoubb :)
2013-2014:| VCE
2015-2018:| Bachelor of Science (Neuroscience) @ UoM
2019-X:| Doctor of Dental Surgery (discontinued)
2019 -2021:| Master of Physiotherapy

Currently: Physiotherapist working at a musculoskeletal clinic. Back pain, sore neck, headaches or any other pain limiting your study? Give me a PM (although please do see your personal health professional first!)

Any questions related to pathways towards studying dentistry or physiotherapy? Gimmi a PM!

lzxnl

  • Victorian
  • ATAR Notes Legend
  • *******
  • Posts: 3432
  • Respect: +215
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #8 on: December 20, 2013, 02:03:27 pm »
+2
I think that learning the theory of chromatography and spectroscopy techniques  is mainly just memory work- consult both textbooks, others' notes etc. So in that sense it is not too bad. What people find difficult is the interpretation of chromatograms, and readouts from the various instruments- which is what is generally given more marks on the exam. So, in order to maximize your marks on the application side of these topics, I would suggest doing selected review questions (some of them are badly written and not likely to appear on an exam) in conjunction with Checkpoints, Neap or Lisachem books that give you really good targeted practice. Personally I found holidays the best time to cover the most content, and leave more application practice to during the term. Hope this helps

I think it would also be helpful to know what exactly goes on in these techniques. Like, for instance, how NMR actually works. They could certainly ask questions on that.
Interpretations of chromatograms, I think, is relatively straightforward in comparison as doing enough practice questions should help you with that. Most of my practice came through Checkpoints and I think it helped.

Thanks guys;

Can someone also please help me with gravimetric analysis. Last week I did all the gravimetric analysis questions, but not in the best of ways (kept making mistakes). So I did some more questions today to make up, and had a bit of trouble. My method of answering these questions are;

- Read the question carefully, find the precipitate, write down a fully balanced equation
- After writing down the equation, write down everything you have
- Use mole ratios to convert whatever you have to what you need

Is that method alright? I don't know why but I'm getting heaps of grav-questions wrong. Any help/tips appreciated!

I think the easiest way of thinking about gravimetric analysis questions is to keep a mental track of where the heck the ions are going. For instance, in last year's chemistry exam, there was a question that asked to find the % by mass of calcium ions in a CaO ore. We were given the mass of calcium oxalate precipitated after treating the calcium oxide with oxalic acid. The simplest way to go about a question like this is to realise that all of the calcium ions in CaO appear in CaC2O4, so you can then easily work out mole ratios. Gravimetric analysis is essentially extended stoichiometry IMO.
2012
Mathematical Methods (50) Chinese SL (45~52)

2013
English Language (50) Chemistry (50) Specialist Mathematics (49~54.9) Physics (49) UMEP Physics (96%) ATAR 99.95

2014-2016: University of Melbourne, Bachelor of Science, Diploma in Mathematical Sciences (Applied Maths)

2017-2018: Master of Science (Applied Mathematics)

2019-2024: PhD, MIT (Applied Mathematics)

Accepting students for VCE tutoring in Maths Methods, Specialist Maths and Physics! (and university maths/physics too) PM for more details

Rod

  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1755
  • The harder the battle, the sweeter the victory
  • Respect: +101
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #9 on: December 24, 2013, 09:34:05 pm »
0
Hey guys,

So I've been stuck in a fairly easy question for a while now:

In this question I have to balance the reaction Cr2O7^(-2) ------- Cr^(3+)

So here is what I did:

Cr207^-2+14h+ +9e-------- Cr^3+ +7h20

What am I doing wrong here??

Thanks!
2013-2014:| VCE
2015-2018:| Bachelor of Science (Neuroscience) @ UoM
2019-X:| Doctor of Dental Surgery (discontinued)
2019 -2021:| Master of Physiotherapy

Currently: Physiotherapist working at a musculoskeletal clinic. Back pain, sore neck, headaches or any other pain limiting your study? Give me a PM (although please do see your personal health professional first!)

Any questions related to pathways towards studying dentistry or physiotherapy? Gimmi a PM!

Homer

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 431
  • Respect: +10
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #10 on: December 24, 2013, 09:37:21 pm »
0
Cr is not balanced
Bachelor of Laws/Engineering

2013 ATAR: 98.65

Specialist Maths [53.06] Maths Methods [48.83] Physics [48.22]

Donuts. Is there anything they can't do?

Rod

  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1755
  • The harder the battle, the sweeter the victory
  • Respect: +101
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #11 on: December 24, 2013, 09:39:32 pm »
0
Cr is not balanced
Yeah sorry that was silly, but apparently it's 6e- and not 9e-. That's the mistake that I've done.
2013-2014:| VCE
2015-2018:| Bachelor of Science (Neuroscience) @ UoM
2019-X:| Doctor of Dental Surgery (discontinued)
2019 -2021:| Master of Physiotherapy

Currently: Physiotherapist working at a musculoskeletal clinic. Back pain, sore neck, headaches or any other pain limiting your study? Give me a PM (although please do see your personal health professional first!)

Any questions related to pathways towards studying dentistry or physiotherapy? Gimmi a PM!

lzxnl

  • Victorian
  • ATAR Notes Legend
  • *******
  • Posts: 3432
  • Respect: +215
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #12 on: December 24, 2013, 09:42:38 pm »
+1
Hey guys,

So I've been stuck in a fairly easy question for a while now:

In this question I have to balance the reaction Cr2O7^(-2) ------- Cr^(3+)

So here is what I did:

Cr207^-2+14h+ +9e-------- Cr^3+ +7h20

What am I doing wrong here??

Thanks!

Something that I rarely do personally, but always helps to help check, is to confirm that the number of electrons balances the total change in oxidation number. Even if you hadn't noticed the glitch of having two chromiums, you should be wondering, where are these nine electrons coming from?
2012
Mathematical Methods (50) Chinese SL (45~52)

2013
English Language (50) Chemistry (50) Specialist Mathematics (49~54.9) Physics (49) UMEP Physics (96%) ATAR 99.95

2014-2016: University of Melbourne, Bachelor of Science, Diploma in Mathematical Sciences (Applied Maths)

2017-2018: Master of Science (Applied Mathematics)

2019-2024: PhD, MIT (Applied Mathematics)

Accepting students for VCE tutoring in Maths Methods, Specialist Maths and Physics! (and university maths/physics too) PM for more details

Homer

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 431
  • Respect: +10
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #13 on: December 24, 2013, 09:44:42 pm »
+1
if you balance the Cr, you'll have +6 charge on the right hand side of the equation, so you would need 6e-(instead of 9e-) on the left hand side to balance the equation
Bachelor of Laws/Engineering

2013 ATAR: 98.65

Specialist Maths [53.06] Maths Methods [48.83] Physics [48.22]

Donuts. Is there anything they can't do?

Rod

  • Victorian
  • Part of the furniture
  • *****
  • Posts: 1755
  • The harder the battle, the sweeter the victory
  • Respect: +101
Re: Rod's Chemistry 3/4 Questions Thread
« Reply #14 on: December 24, 2013, 09:46:00 pm »
0
Something that I rarely do personally, but always helps to help check, is to confirm that the number of electrons balances the total change in oxidation number. Even if you hadn't noticed the glitch of having two chromiums, you should be wondering, where are these nine electrons coming from?
Still don't get it, sorry.

So the reactant side should have a total charge of -2+ 14= 12
And the products should have a total charge of +3

12-9=3

So shouldn't we add 9 electrons to the reactants?
2013-2014:| VCE
2015-2018:| Bachelor of Science (Neuroscience) @ UoM
2019-X:| Doctor of Dental Surgery (discontinued)
2019 -2021:| Master of Physiotherapy

Currently: Physiotherapist working at a musculoskeletal clinic. Back pain, sore neck, headaches or any other pain limiting your study? Give me a PM (although please do see your personal health professional first!)

Any questions related to pathways towards studying dentistry or physiotherapy? Gimmi a PM!