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March 29, 2024, 02:03:22 am

Author Topic: VCE Chemistry Question Thread  (Read 2313208 times)  Share 

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Blondie21

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Re: VCE Chemistry Question Thread
« Reply #645 on: April 18, 2014, 05:19:03 pm »
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Methoxymethane. Dimethyl ether is also an acceptable name.

You aren't expected to name ethers in the VCE course.

Thanks :)

Do we need to know about the carbonyl functional group, aldehydes and kentones?
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Aurelian

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Re: VCE Chemistry Question Thread
« Reply #646 on: April 18, 2014, 05:32:54 pm »
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Thanks :)

Do we need to know about the carbonyl functional group, aldehydes and kentones?

You are not required to be able to name aldehydes and ketones, but you do need to know what they are, especially in the context of the oxidation of alcohols (which can generate aldehydes, ketones and/or carboxylic acids).
« Last Edit: April 18, 2014, 05:35:41 pm by Aurelian »
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thushan

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Re: VCE Chemistry Question Thread
« Reply #647 on: April 18, 2014, 07:09:31 pm »
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You are not required to be able to name aldehydes and ketones, but you do need to know what they are, especially in the context of the oxidation of alcohols (which can generate aldehydes, ketones and/or carboxylic acids).

I disagree - I think it's helpful to know what they are to get a better picture of what goes on, but that is quite peripheral knowledge, I highly doubt that that is assessable.
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Aurelian

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Re: VCE Chemistry Question Thread
« Reply #648 on: April 18, 2014, 07:11:57 pm »
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I disagree - I think it's helpful to know what they are to get a better picture of what goes on, but that is quite peripheral knowledge, I highly doubt that that is assessable.

? I also recommended knowing what they are? :S
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Jawnle

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Re: VCE Chemistry Question Thread
« Reply #649 on: April 19, 2014, 12:47:15 pm »
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What's the theory behind a non-polar solvent dissolving in a non-polar solute?

I understand how "like dissolves in like", and how polar solvents can dissolve in polar solutes because of their partial pos/neg charges but what about for non-polar, when all the charges are equal?
Thanks

thushan

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Re: VCE Chemistry Question Thread
« Reply #650 on: April 19, 2014, 01:09:05 pm »
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Non-polar substances can dissolve in other non-polar solvents because the two substances exhibit dispersion forces with each other.
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Jawnle

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Re: VCE Chemistry Question Thread
« Reply #651 on: April 19, 2014, 01:15:52 pm »
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Non-polar substances can dissolve in other non-polar solvents because the two substances exhibit dispersion forces with each other.

Is it because of the instantaneous dipoles created from dispersion forces?

lzxnl

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Re: VCE Chemistry Question Thread
« Reply #652 on: April 19, 2014, 02:44:36 pm »
+1
What's the theory behind a non-polar solvent dissolving in a non-polar solute?

I understand how "like dissolves in like", and how polar solvents can dissolve in polar solutes because of their partial pos/neg charges but what about for non-polar, when all the charges are equal?
Thanks

I made another post in the chem forum about this
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Snorlax

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Re: VCE Chemistry Question Thread
« Reply #653 on: April 19, 2014, 02:46:05 pm »
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Is the base peak the same as the parent molecular ion in mass spectroscopy?
Also is the base peak/parent molecular ion the one with the highest intensity?

Thanks
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lzxnl

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Re: VCE Chemistry Question Thread
« Reply #654 on: April 19, 2014, 02:50:20 pm »
+2
Is the base peak the same as the parent molecular ion in mass spectroscopy?
Also is the base peak/parent molecular ion the one with the highest intensity?

Thanks

Base peak = peak with highest intensity
Which isn't always the parent molecular ion (it can be, no guarantee)
Parent molecular ion is the peak from the molecule you're analysing (i.e. the one before all of that fragmentation)
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Blondie21

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Re: VCE Chemistry Question Thread
« Reply #655 on: April 19, 2014, 05:42:37 pm »
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I don't understand the formula for finding the number of double bonds in a molecule. I would normally draw the molecule but this methods seems quicker.

Anyways, to find C3H5Cl, I would:

(7) - (6) + 0
-----------------
         2

Even though it should have one double bond, not 1/2

What am I doing wrong?
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Snorlax

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Re: VCE Chemistry Question Thread
« Reply #656 on: April 19, 2014, 05:58:13 pm »
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I never got my head around dilution, so can someone clarify? :/

So I have a stock standard solution: 1000mg/100mL  of caffeine
I want to make concentrations of 5mg/100ml, 10mg/100ml and 20mg/100ml caffeine.

Say for the first concentration I want to obtain (5mg/100ml), do i simply get like 0.5mL of the standard (5mg/0.5mL), and then dilute it into 100mL?
Is that how it works? o.o
Or is my logic wrong. hahhaha


Thanks!
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Rishi97

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Re: VCE Chemistry Question Thread
« Reply #657 on: April 19, 2014, 06:16:45 pm »
+2
I don't understand the formula for finding the number of double bonds in a molecule. I would normally draw the molecule but this methods seems quicker.

Anyways, to find C3H5Cl, I would:

(7) - (6) + 0
-----------------
         2

Even though it should have one double bond, not 1/2

What am I doing wrong?

Hey

I have attached the actual formula. I think you were forgetting the a+1
a = number of Carbon atoms in the compound
b = number of Hydrogen atoms in the compound
c = number of Nitrogen atoms in the compound
 f = number of Halogen atoms in the compound
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Re: VCE Chemistry Question Thread
« Reply #658 on: April 19, 2014, 06:35:33 pm »
+1
I never got my head around dilution, so can someone clarify? :/

So I have a stock standard solution: 1000mg/100mL  of caffeine
I want to make concentrations of 5mg/100ml, 10mg/100ml and 20mg/100ml caffeine.

Say for the first concentration I want to obtain (5mg/100ml), do i simply get like 0.5mL of the standard (5mg/0.5mL), and then dilute it into 100mL?
Is that how it works? o.o
Or is my logic wrong. hahhaha



Thanks!
So initially, you have 1000mg/100mL, then after dilution, you have 5 mg/100 mL, you can see that 1000/5 = 200 . If concentration decrease by 200 folds, volume must have increased by 200 folds. Hence, 100 x 200 = 20 000 mL i.e if you fill the volume up to 20 00mL (adding 19 900 mL), you get a concentration of 5 mg/100mL.
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rhinwarr

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Re: VCE Chemistry Question Thread
« Reply #659 on: April 19, 2014, 06:58:17 pm »
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Do double bonds count as functional groups?