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March 29, 2024, 02:28:12 am

Author Topic: VCE Chemistry Question Thread  (Read 2313232 times)  Share 

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h.dave

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Re: VCE Chemistry Question Thread
« Reply #8475 on: March 11, 2020, 08:07:00 pm »
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Hi, I am a year 12 doing unit 3 and 4 of Chemistry and it's not doing so well. My first SAC started off really bad and the test results were equally as bad. How do I improve and make myself feel better? And tell my parents my really bad scores?  :( :(

Geoo

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Re: VCE Chemistry Question Thread
« Reply #8476 on: March 11, 2020, 08:42:11 pm »
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What is the difference between heat of combustion, and molar heat of combustion?
I'm a bit confused... and do they have different symbols?
2020: VCE 93.2
2022: BSci/Arts (Chemistry/Pharmacology and French)@Monash

hums_student

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Re: VCE Chemistry Question Thread
« Reply #8477 on: March 11, 2020, 08:45:19 pm »
+8
Hi, I am a year 12 doing unit 3 and 4 of Chemistry and it's not doing so well. My first SAC started off really bad and the test results were equally as bad. How do I improve and make myself feel better? And tell my parents my really bad scores?  :( :(
Hello, I can relate. I did badly in 1/2 chem all year, almost got kicked out of the class (the school sent me multiple emails telling me to drop the subject), and on my first 3/4 chem SAC I got about 15% below the school average. What I found help me improve was to get together with some friends or even just people I sort of know, and studying with them to learn from their techniques and also to make sure I don't lag behind. Another thing was to get feedback on everything - absolutely everything. I regularly booked appointments (either during lunchtime, before/after school, or during my free periods) with various chem teachers and more or less badgered them into correcting my work. I made sure to do all of the chapter review questions in the textbook, and also googled for more worksheets once I've exhausted what the school has given me.

Before each SAC, I'd make sure to do at least three practice SACs under timed conditions, mark it myself, then give it to a teacher to mark as well, before sitting down with the teacher so that they can go through every single question with me. After each SAC, I'd sit down with a teacher again just to go through everything. Towards the end of term 3, I was sending my (unfortunate) chem teacher about 4-5 emails a week asking him to check my work.

Another thing which worked for me was to keep track of all the mistakes I made. It really helped me to avoid making the same mistakes in the future.

Good luck!
2019-21: Bachelor of Arts (Politics & Int'l Relations / Economics)

Evolio

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Re: VCE Chemistry Question Thread
« Reply #8478 on: March 12, 2020, 01:40:51 pm »
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Hey,

Just a Yr 11 unit 1/2 chem student here. I have a chem sac this week including stuff on moles.
Is there an ideal way which we should be setting up our scientific calculator cos I have a feeling that mine isn't set properly cos it isn't giving me the right answers.

For example, the textbook says that if you enter 60x Avogadro's number, then you should get 3.06 x 10^25 but my calculator gives me 3.16 x 10^25.

Thanks in advance!
Hey Snow Leopard!
Have you used the correct button for the exponential 10^23? I found that I was using the wrong exponential button and it was giving me the wrong answers as well. Which calculator are you using and are you able to provide a picture about what buttons you have typed to give your answer?

What is the difference between heat of combustion, and molar heat of combustion?
I'm a bit confused... and do they have different symbols?
Hey Geoo!
Heat of combustion just refers to the amount of energy produced while molar heat of combustion specifically refers to how much energy is produced per mol.
They have the same symbols, that is the delta H.

sandywu

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Re: VCE Chemistry Question Thread
« Reply #8479 on: March 14, 2020, 08:32:45 am »
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Hi  I was wondering if anyone could help me? In the heinamen textbook 3/4 chapter review 4.3, I was wondering in Q4, why the H+ ion is not considered as undergoing reduction as it is oxidised from H+ (aq)--> H20(l)? THe full equation is:  NO –(aq) + H+(aq) + Cu(s) → NO(g) + H O(l) + Cu2+(aq)

Evolio

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Re: VCE Chemistry Question Thread
« Reply #8480 on: March 14, 2020, 09:00:02 am »
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Hey Sandy!
It's best to look at the oxidation numbers for these questions where it may be a but unclear what is undergoing oxidation and reduction.
We can see that the Cu(s) is converted to Cu2+(ag) where the Cu(s) has an oxidation number of 0 since it is a pure compound and the Cu2+ (aq) has an oxidation number of +2, where 0 to +2 is oxidation since there is an increase in oxidation number. Hence, copper is the one undergoing oxidation (it's been oxidised).

If we look at H+(aq) to H2O(l), we can see that there has been no change in oxidation number which means that no reduction or oxidation has taken place thus it can't have been oxidised.
This is because H+(aq) has an oxidation number of +1 and in H2O it also has an oxidation number of +1 so the oxidation numbers have not changed.

Also note that being oxidised means undergoing oxidation (not reduction which you have stated).

Hope this helps!
« Last Edit: March 14, 2020, 09:35:29 am by Evolio »

Snow Leopard

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Re: VCE Chemistry Question Thread
« Reply #8481 on: March 14, 2020, 10:57:05 pm »
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Hey Snow Leopard!
Have you used the correct button for the exponential 10^23? I found that I was using the wrong exponential button and it was giving me the wrong answers as well. Which calculator are you using and are you able to provide a picture about what buttons you have typed to give your answer?
Hey Evolio!
I've attached a pic of scientific calculator. I'm just typing in the numbers and using the to the x power of button to write 10^23 for example.

Evolio

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Re: VCE Chemistry Question Thread
« Reply #8482 on: March 15, 2020, 07:59:05 am »
+3
So, you've typed 60 x 6.02 x 10^23 with the x to the power of the shaded square button... Yeah, you should get 3.61 x 10^25 which is what I get on my calculator. Have you tried it again and again with no existing calculations i.e pressing the on button for every new calculation?
If it's still giving you a different answer, I think you should check with your teacher and hopefully they'll be able to tell you what the problem is.
« Last Edit: March 15, 2020, 08:01:54 am by Evolio »

Snow Leopard

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Re: VCE Chemistry Question Thread
« Reply #8483 on: March 15, 2020, 04:26:28 pm »
+1
So, you've typed 60 x 6.02 x 10^23 with the x to the power of the shaded square button... Yeah, you should get 3.61 x 10^25 which is what I get on my calculator. Have you tried it again and again with no existing calculations i.e pressing the on button for every new calculation?
If it's still giving you a different answer, I think you should check with your teacher and hopefully they'll be able to tell you what the problem is.
It works! I must've been putting it in wrong before or something.
Thank you!!!

cherryblossoms

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Re: VCE Chemistry Question Thread
« Reply #8484 on: March 23, 2020, 12:02:49 am »
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Hey, I have a question about the term 'accuracy' for scientific investigations. If I don't know the 'true' value for a measurement, would it be right to say it is not possible to determine the accuracy of the measurements? Or is the 'true' value what I measured, and if I put that value in my results, that would be high accuracy?

How do we find the 'true value'?

Evolio

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Re: VCE Chemistry Question Thread
« Reply #8485 on: March 23, 2020, 07:10:48 am »
+4
Hello cherryblossoms.

Yes, if you don't know the true value, you can say that as no comparisons can be made between your experimental value and true value. What is your experiment by the way?  Has it been done before?  Because if it has, there will be a true value and vice versa.

The true value is not what you measured, it is a value that has been obtained under accurate conditions for your experiment, done by another scientific researcher for example.

Here is a very helpful link from VCAA that talks about accuracy in regards to your question :

https://www.vcaa.vic.edu.au/curriculum/vce/vce-study-designs/chemistry/advice-for-teachers/Pages/MeasurementinScienceMeasurementTerms.aspx
« Last Edit: March 23, 2020, 07:14:05 am by Evolio »

Geoo

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Re: VCE Chemistry Question Thread
« Reply #8486 on: March 24, 2020, 04:05:53 pm »
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For the life of me, I can't figure out the oxidation number of N and Cr in ammonium dichromate.


Could someone show me.
Thank you
2020: VCE 93.2
2022: BSci/Arts (Chemistry/Pharmacology and French)@Monash

Evolio

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Re: VCE Chemistry Question Thread
« Reply #8487 on: March 24, 2020, 05:57:49 pm »
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Hey Geoo.
I was so confused when I looked at this lol.
But then I found this great video that shows you how to find the oxidation numbers step by step!: https://www.youtube.com/watch?v=5FU5CQI_q1w

From this video it said that NH4 (ammonium) is an ion with a charge of +1. H has an oxidation number of +1.
So: N+4=-1. That means, N has an oxidation number of -3.
-3 x 2 = -6. This is the oxidation number so far, in regards to the ammonium
Oxygen has an oxidation number of -2 and according to the video, dichromate has an oxidation number of -2.
So: 2Cr - 14= -2.
2Cr = 12 Cr=+6

To be honest with you, I highly doubt that VCAA will ask you to find the oxidation number of this but then I guess, you never know so it's good to know this stuff!  ;D


« Last Edit: March 24, 2020, 05:59:49 pm by Evolio »

J_Rho

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Re: VCE Chemistry Question Thread
« Reply #8488 on: March 26, 2020, 12:32:13 pm »
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Hey chem kids! Anyone got a good simple definition of polar molecules and nonpolar molecules?
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colline

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Re: VCE Chemistry Question Thread
« Reply #8489 on: March 26, 2020, 01:12:32 pm »
+5
Hey chem kids! Anyone got a good simple definition of polar molecules and nonpolar molecules?

A simple definition is that polar molecules have charges that's not evenly distributed while nonpolar molecules are evenly distributed.


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