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March 29, 2024, 09:59:53 am

Author Topic: HSC Chemistry Question Thread  (Read 1040673 times)  Share 

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angela99

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Re: Chemistry Question Thread
« Reply #330 on: May 24, 2016, 06:53:07 pm »
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my teacher constantly tells me that my prac sections in the exam are my weakest.. im not really sure how to study the pracs we do in class or how to write notes on them
any tips or layouts?

RuiAce

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Re: Chemistry Question Thread
« Reply #331 on: May 24, 2016, 07:28:09 pm »
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my teacher constantly tells me that my prac sections in the exam are my weakest.. im not really sure how to study the pracs we do in class or how to write notes on them
any tips or layouts?


Studying for pracs is a matter of:
- Knowing the aim
- Knowing the method
- Only knowing results if its relevant (however this is often more than not)
- Knowing limitations to the experiment
- Identifying controls/variables, as well as relating validity/reliability/discussion
Hey!

I think that, generally, there is little to study when it comes to chemistry pracs. Most of the time, you aren't being assessed on specific, actual knowledge of the course; rather, on your analytical skills, your ability to form a discussion and sometimes your ability to do calculations.

Other than being comfortable with a titration, in case you are asked to do one, I think that the main this to worry about is being able to write balanced chemical formulas, use equations from throughout the course, and understanding what accuracy, reliability and validity are. This latter point is especially important, in case you are asked (as often occurs) to write out a discussion for your prac.

You need to be able to write a risk assessment (risk, precaution, response) and be able to graph any results you find.

I think that's about it; I didn't elaborate on each of the above notes because I figured that you probably understand most of them, but if there is any part of this answer that I can expand on (accuracy, reliability and validity for example) please let me know! Happy to help out however I can.

Jake
...

ProfLayton2000

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Re: Chemistry Question Thread
« Reply #332 on: June 02, 2016, 09:01:27 pm »
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How do you assess the validity of an experiment?

jakesilove

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Re: Chemistry Question Thread
« Reply #333 on: June 02, 2016, 09:32:11 pm »
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How do you assess the validity of an experiment?

Hey there!

For validity, you're essentially asking yourself did the experiment test what you were trying to test. In other words, did the set up actually answer the aim of the experiment?

This often takes into account things like whether or not you have controlled your variables, whether there may be any impurities in your substances, whether you put the right things in the right place and whether you used the correct kind of glassware. An example would be the experiment where you test the specific heat capacity of specific substances (ethanol etc.). Most of the heat DOESN'T get transferred into the water; most of it is lost to the environment! So, you're not REALLY testing what you're trying to test, greatly limiting the validity of the experiment.

If you have any specific questions, regarding specific pracs, let me know! Hope this helped :)

Jake
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browny2409

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Re: Chemistry Question Thread
« Reply #334 on: June 04, 2016, 03:15:32 pm »
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Hi, there is a dotpoint about the reliability of the sulphate fertiliser prac - what exactly else would you talk about for reliability other then repeatability?

Thanks
Nathan

RuiAce

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Re: Chemistry Question Thread
« Reply #335 on: June 04, 2016, 04:00:28 pm »
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Hi, there is a dotpoint about the reliability of the sulphate fertiliser prac - what exactly else would you talk about for reliability other then repeatability?

Thanks
Nathan

I would talk about grammar.

Just kidding :P But not really - in a first hand investigation, repetition is the main requirement for reliability to be achieved. The more you repeat the experiment, the more reliable it is.

As for a dot point, yes. Refer to Chemical Monitoring and Management section 3. The dot points are #3 and #4 of the third column.

(Since your results involve a numeric analysis, if your figures are all over the place then that's clearly not as reliable as figures such as 70g, 72g and 69.5g. So if validity or accuracy crumbles, in this case reliability may also be damaged. This is probably the reason why reliability has a seperate dot point for this practical.)
« Last Edit: June 04, 2016, 04:02:54 pm by RuiAce »

relativity1

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Re: Chemistry Question Thread
« Reply #336 on: June 06, 2016, 02:35:15 pm »
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couple of questions
-how to improve accuracy/reliability of the molar heat of combustion prac
-why weak acids have lower molar heats of neutralization than strong acids (something to do with ionisation i think)

Adriaclya

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Re: Chemistry Question Thread
« Reply #337 on: June 06, 2016, 03:12:30 pm »
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Hi guys, i am really confused about moles, molar masses and such. Can someone please enlighten me?
Thanks!

RuiAce

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Re: Chemistry Question Thread
« Reply #338 on: June 06, 2016, 05:31:59 pm »
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couple of questions
-how to improve accuracy/reliability of the molar heat of combustion prac
-why weak acids have lower molar heats of neutralization than strong acids (something to do with ionisation i think)

Reliability is trivial. Keep repeating the experiment.
Accuracy can be a bit harder though. For this prac, accuracy ties down to validity a lot. Most of the time your molar heat of combustion prac will be quite noticeably inaccurate because heat loss to the surroundings is so hard to perfectly control. It's almost impossible to create the perfect environment in the laboratory to perform a fully accurate experiment here.

Hi guys, i am really confused about moles, molar masses and such. Can someone please enlighten me?
Thanks!
That doesn't really give me much direction as to where you should be headed.

Avogadro's number: 6.022 * 1023 = NA

1 mol of a substance = Avogadro's number times the number of molecules of that substance.
I.e. 1 mol of O2 is the same as saying you have  6.022 * 1023 oxygen molecules present.

The fundamental equation of chemistry is n=m/M where m is the mass of a substance present, and M is the molar mass of said substance. The molar mass can be extracted straight off the periodic table.

Johny1234567

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Re: Chemistry Question Thread
« Reply #339 on: June 12, 2016, 01:52:39 am »
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Analyse the industrial consideratinos of the Solvay Process. (7 marks)

Critically analyse the environmental concerns posed by the Solvay Process and the way in which these are addressed. (7 marks)

ProfLayton2000

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Re: Chemistry Question Thread
« Reply #340 on: June 15, 2016, 05:05:23 pm »
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Hi there,

"Chemists are involved in monitoring and managing the environment. They deal with the reactants, products and conditions of reactions that occur in the environment around us. To do this they identify and measure chemicals around us.  Discuss equipment and methods used by chemists to monitor our environment" (7 marks)

What do you suggest I include in my answer (and could you recommend a structure )?

jakesilove

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Re: Chemistry Question Thread
« Reply #341 on: June 15, 2016, 08:06:37 pm »
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Hi there,

"Chemists are involved in monitoring and managing the environment. They deal with the reactants, products and conditions of reactions that occur in the environment around us. To do this they identify and measure chemicals around us.  Discuss equipment and methods used by chemists to monitor our environment" (7 marks)

What do you suggest I include in my answer (and could you recommend a structure )?

Hey!

This is an awfully vague, slightly absurd question to be asked. Still, for a 7 marker, it's a beast of a thing so it's important that we are able to tame it! I would probably recommend talking about at least two big hitter issues, discussing what they are, how scientists monitor it and why scientists monitor it.

The most obvious choices are the production of CFCs (and depletion of Ozone) and polluting waterways. In terms of structure, I would start with a quick introduction (Scientists monitor the environment and use chemical equations etc. etc. to protect etc. etc.). Then, throw a subheading "Ozone" in. Talk about what Ozone is, why it's important, what CFCs are, why they were significant, how we detected them, change over time etc. MAKE SURE TO TALK ABOUT EQUIPMENT used to monitor this process: This is specifically in the question, and forgetting to do so could lose you marks. Then, I'd do the same thing with waterways. Be fairly brief; you want to get across the fact that chemicals are scary, and can have huge impacts on our environment, and that monitoring them is the only way to be sure we don't all die. At the same time, mention specific information if you can (dates, equipment, processes). It's possible that talking about two separate things is a bit much; perhaps one would be sufficient. Either way, as long as you get the point across you'll get the marks! If you feel like writing up a response, I'd be happy to take a look at it :)

Let me know if I can elaborate on any of this or answer any other questions!

Jake
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katherine123

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Re: Chemistry Question Thread
« Reply #342 on: June 17, 2016, 02:37:13 am »
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why is the answer B?

Jakeybaby

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Re: Chemistry Question Thread
« Reply #343 on: June 17, 2016, 08:15:30 am »
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why is the answer B?
It's irrelevant to the fact that one is weak and one is strong. It's due to both acids having the same concentration, therefore will both be titrated by the base at the same rate. The equivalence point will be the same as the same about of base will be needed to reach equivalence.
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jakesilove

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Re: Chemistry Question Thread
« Reply #344 on: June 17, 2016, 09:06:37 am »
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It's irrelevant to the fact that one is weak and one is strong. It's due to both acids having the same concentration, therefore will both be titrated by the base at the same rate. The equivalence point will be the same as the same about of base will be needed to reach equivalence.

Absolutely on point! Think about it this way: When you're doing the maths (ie. C=n/v, moles=mass/molar mass etc.), the 'strong/weak' nature of the acid doesn't come into play at all. All you care about is the concentration, and the molar ratio, which is exactly the same between the two substances! Thanks for the response Jakey, quality stuff.

Jake
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