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March 28, 2024, 11:20:57 pm

Author Topic: VCE Chemistry Question Thread  (Read 2313099 times)  Share 

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ardria

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Re: VCE Chemistry Question Thread
« Reply #6435 on: July 14, 2017, 06:51:22 pm »
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I'm going to try and explain this with the example of 1,2dichloroethane. The molecule will be slightly negative where the chlorine atoms are. If this is the cis isomer, both chlorine atoms are on the same side so this will mean that overall the molecule will be more negative on that side. Whereas in the trans isomer the chlorine atoms will be on different sides and so the resulting polarity of the molecule will be quite different.

Hope this helps :)

Could you say that trans-1,2-dichloroethane is less polar and cis is more polar/a polar molecule? And this is what gives the different properties?
« Last Edit: July 14, 2017, 06:56:15 pm by ardria »

ardria

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Re: VCE Chemistry Question Thread
« Reply #6436 on: July 14, 2017, 06:59:50 pm »
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Here is a question with the written explanation to the right (the correct answer is B not C).

http://imgur.com/a/TodDf

Why is it CH2 and not C2H4, because isn't the latter ethene?

Thanks in advance :)
« Last Edit: July 14, 2017, 07:04:57 pm by ardria »

VanillaRice

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Re: VCE Chemistry Question Thread
« Reply #6437 on: July 14, 2017, 07:11:41 pm »
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Here is a question with the written explanation to the right (the correct answer is B not C).

http://imgur.com/a/TodDf

Why is it CH2 and not C2H4, because isn't the latter ethene?

Thanks in advance :)
Not sure why they used -CH2-, but if you think about it, C2H4 is basically a multiple of CH2. And since this is a multiple choice question which asks for an approximate answer, I would say that whether you used CH2 or C2H4 doesn't really matter, since you end up with the answer anyway. 
Furthermore, if you think about a polyethene molecule - in a general sense, it doesn't really matter if you think about it in terms of being a polymer -CH2- or -C2H4- units. But if the question wanted you to write the chemical formula for polyethene, using C2H4 would be more correct.

EDIT: The worked solution probably did it that way to simplify things, since you only need to worry about 1 carbon. If you used C2H4 (M = 28) - after dividing 40,000/28, you would have to multiply by two since there are two carbons per ethene monomer.
« Last Edit: July 14, 2017, 07:14:32 pm by VanillaRice »
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Novashock

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Re: VCE Chemistry Question Thread
« Reply #6438 on: July 14, 2017, 10:04:53 pm »
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Hey Guys!!
So i didn't know whether to make this a new post so i just posted this here but anyways im currently in year 11 and i'm doing psych as my 3/4, and getting towards the end of the year, i'm really starting to focus a lot more on it (seriously, haven't touched anything else this holiday, going for 46+ hopefully!), which means i'm not really focusing on other subjects as much as i should be. This is on top of the fact that my teacher has trouble teaching (like conveying knowledge and engaging the class, he's actually shocking, why i literally was considering dropping chem AND bio) and sadly his daughters been diagnosed with some disease, and hes gotta leave school 3 days a week to get her to treatment. I try to teach myself chem but after methods i feel the least into this and can't sit down for too long doing this.

So basically what i was wondering was what are your best tips to learn/study chem for someone who doesn't really get it (averaging 70-80% which isnt too bad but i wanna do better tbh). THANKS !!!!
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ringring

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Re: VCE Chemistry Question Thread
« Reply #6439 on: July 15, 2017, 02:28:55 pm »
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Hey!
Can anyone help me out with this question? I know that decreased temp=higher voltage but I'm having a bit of trouble linking it back to chemistry concepts...

How does temperature affect the voltage of a galvanic cell?
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Gogo14

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Re: VCE Chemistry Question Thread
« Reply #6440 on: July 15, 2017, 04:05:44 pm »
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Hey!
Can anyone help me out with this question? I know that decreased temp=higher voltage but I'm having a bit of trouble linking it back to chemistry concepts...

How does temperature affect the voltage of a galvanic cell?
It's got to do with Nerst's equation. E nought is only the voltage of a half cell under standard conditions (i.e. 25degrees), but when you deviate from standard conditions, E nought cannot be used to calculate the voltage of a galvanic cell. Therefore you have to calculate it with Nernst's equation (but it is not in the vce course).
https://en.wikipedia.org/wiki/Nernst_equation
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zxcvbnm18

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Re: VCE Chemistry Question Thread
« Reply #6441 on: July 16, 2017, 03:39:47 pm »
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why does the anode of a metal hydride rechargable cell have to be a hydrogen abosorbing metal? Thnx in advance

dx1sy

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Re: VCE Chemistry Question Thread
« Reply #6442 on: July 17, 2017, 05:43:24 pm »
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Hi!

Can someone please explain why increasing the concentration of an electrolyte increases the amount of metal deposited at the cathode during electroplating? Thanks!!

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Re: VCE Chemistry Question Thread
« Reply #6443 on: July 17, 2017, 05:57:21 pm »
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Hi!

Can someone please explain why increasing the concentration of an electrolyte increases the amount of metal deposited at the cathode during electroplating? Thanks!!
Concentration= moles/litre
so increasing the concentration increases the amount of moles of reactant, which increases the number of moles of product in accordance with the molar ratio in the equation for your redox reaction

VanillaRice

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Re: VCE Chemistry Question Thread
« Reply #6444 on: July 17, 2017, 07:47:58 pm »
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why does the anode of a metal hydride rechargable cell have to be a hydrogen abosorbing metal? Thnx in advance
Let's define MH as a metal hydride, where M = metal.
Using the example of a Lithium-metal hydride battery, the discharge half equation at the anode would be:

As you can see, the metal hydride donates its hydrogen atom to the hydroxide ion to form a water molecule. Now, in order to recharge the battery, the above reaction must be reversed:

Therefore, the metal in a metal hydride must be able to accept hydrogen atoms in order to be recharged (although I'm not sure the metal hydride would exist in the first place if the metal didn't accept hydrogen atoms).

I hope I've interpreted your question correctly and this helps  :)
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dani_b19

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Re: VCE Chemistry Question Thread
« Reply #6445 on: July 22, 2017, 02:29:59 pm »
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Hi,
Can someone please help me with this question??

A certain brand of drinking chocolate, which claims to be high in calcium and 99% fat free, states on the label that by adding only hot water in the correct proportion to the contents of a sachet, the concentration of calcium will be 62.5 mg per 100mL of prepared drink.
What volume of this hot chocolate drink would supply and adult male with the total amount of his recommended daily intake of 800 mg of calcium?

Thank you :)

Shadowxo

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Re: VCE Chemistry Question Thread
« Reply #6446 on: July 22, 2017, 02:41:58 pm »
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Hi,
Can someone please help me with this question??

A certain brand of drinking chocolate, which claims to be high in calcium and 99% fat free, states on the label that by adding only hot water in the correct proportion to the contents of a sachet, the concentration of calcium will be 62.5 mg per 100mL of prepared drink.
What volume of this hot chocolate drink would supply and adult male with the total amount of his recommended daily intake of 800 mg of calcium?

Thank you :)
weight/volume (ie concentration) is the same for a 100mL sample, and an V mL sample (unknown volume)
So (weight in mg) / (Volume in mL)= 62.5 mg/100 mL
weight = 800 mg
800/V = 62.5/100
V=800*100/62.5 = 1,280 mL

Alternatively, you need 800/62.5 *100mL of drink = 1,280mL (quicker but less intuitive and harder to explain)
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usernameincorrect

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Re: VCE Chemistry Question Thread
« Reply #6447 on: July 25, 2017, 10:37:57 pm »
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Ok, so this question is with ref to naming hydrocarbons in the Chem checkpoints book. For 1-chloroprop-2-ene, which is the way its written in the answers, shouldn't it be 3-chloroprop-1-ene, because the double bond has a higher priority compared to the halogen, and so numbering begins there? I understand the book is trying to get the lowest overall numbers, but im confused. Please help, cheers

kalopsia

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Re: VCE Chemistry Question Thread
« Reply #6448 on: July 26, 2017, 07:16:47 am »
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Ok, so this question is with ref to naming hydrocarbons in the Chem checkpoints book. For 1-chloroprop-2-ene, which is the way its written in the answers, shouldn't it be 3-chloroprop-1-ene, because the double bond has a higher priority compared to the halogen, and so numbering begins there? I understand the book is trying to get the lowest overall numbers, but im confused. Please help, cheers

Came across that question as well and I got the same answer as you. I also asked my teacher, and we think checkpoints is wrong.
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usernameincorrect

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Re: VCE Chemistry Question Thread
« Reply #6449 on: July 26, 2017, 08:46:16 pm »
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Came across that question as well and I got the same answer as you. I also asked my teacher, and we think checkpoints is wrong.

Oh wow what a coincidence! It's good to hear that :) feeling more confident now