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March 29, 2024, 09:21:27 pm

Author Topic: VCE Chemistry Question Thread  (Read 2313733 times)  Share 

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swagsxcboi

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Re: VCE Chemistry Question Thread
« Reply #675 on: April 19, 2014, 08:41:14 pm »
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for the reaction between butane and chlorine, I'd get a chlorobutane. How do I know the states of butane and chlorobutane?
I don't think they assess states for organic chem
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Blondie21

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Re: VCE Chemistry Question Thread
« Reply #676 on: April 19, 2014, 09:08:46 pm »
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Finish this sentence (This is about DNA)

The encricled group is called a ___________________.
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vox nihili

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Re: VCE Chemistry Question Thread
« Reply #677 on: April 19, 2014, 09:24:36 pm »
+1
Finish this sentence (This is about DNA)

The encricled group is called a ___________________.

This sounds like there's a photo missing... hahaha
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Blondie21

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Re: VCE Chemistry Question Thread
« Reply #678 on: April 19, 2014, 10:26:22 pm »
+6
This sounds like there's a photo missing... hahaha

oh hahah I thought 'encricled' might be a chem term LOL
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Rishi97

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Re: VCE Chemistry Question Thread
« Reply #679 on: April 20, 2014, 10:17:50 am »
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The compound has the molecular formula C57H100O6 (Mr= 880 g/mol)
How many carbon-to-carbon bonds are present in this compound? Explain your answer
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Rishi97

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Re: VCE Chemistry Question Thread
« Reply #680 on: April 20, 2014, 11:10:55 am »
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C57H115OH

116-100 = 16
16/2 = 8

There are eight double bonds present. For every C=C double bond, two hydrogen atoms are lost. Therefore, because the general formula for 57 carbon atoms (given no double bonds) reveals we need 116 hydrogen atoms, and only 100 are present, means 16 atoms of hydrogen have been lost. As we mentioned, a C=C double bond exists for every two hydrogens lost. 16 divided by 2 gives 8. 8 double bonds are present in the compound.

The answer says 5  carbon-to-carbon double bonds.
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Yacoubb

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Re: VCE Chemistry Question Thread
« Reply #681 on: April 20, 2014, 11:16:43 am »
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The answer says 5  carbon-to-carbon double bonds.

Yeah sorry I misread the compound itself! Sorry!

Yacoubb

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Re: VCE Chemistry Question Thread
« Reply #682 on: April 20, 2014, 11:24:08 am »
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The answer says 5  carbon-to-carbon double bonds.

Okay got it:

The compound's molecular formula: C57H100O6

Consider the oxygen atoms as hydrogens
In this way, we have C57H106

Now, the general formula for an alkane is CnH2n+2

C57H116

Now, 116-106 = 10
10/2 = 5 C=C double bonds

thushan

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Re: VCE Chemistry Question Thread
« Reply #683 on: April 20, 2014, 12:06:40 pm »
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Nah - when you work out the number of double bonds + rings in the compound, you ignore O atoms:

so C57H100O6 has the same number of double bonds + rings as C57H100.

Since C57H116 is the saturated alkane, it follows that, since you take of 2 H atoms for ever double bond you form,  there are (116-100)/2= 8 double bonds + rings in the structure.

Check the question again to see if there are any known double bonds and rings in the structure. Perhaps out of the 8 double bonds + rings, 5 would be C=C double bonds. There could be C=O double bonds too, remember.
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Yacoubb

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Re: VCE Chemistry Question Thread
« Reply #684 on: April 20, 2014, 12:18:51 pm »
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Nah - when you work out the number of double bonds + rings in the compound, you ignore O atoms:

so C57H100O6 has the same number of double bonds + rings as C57H100.

Since C57H116 is the saturated alkane, it follows that, since you take of 2 H atoms for ever double bond you form,  there are (116-100)/2= 8 double bonds + rings in the structure.

Check the question again to see if there are any known double bonds and rings in the structure. Perhaps out of the 8 double bonds + rings, 5 would be C=C double bonds. There could be C=O double bonds too, remember.

Thanks thushan! Do you know if there are any rules regarding this that we should be familiar of? Perhaps an explanation or even a link to one would be appreciated! :)

Blondie21

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Re: VCE Chemistry Question Thread
« Reply #685 on: April 20, 2014, 06:55:34 pm »
+1
alkene + h20 ->

is the catalyst H+ or H3PO4?

And according to the text book, this is a hydrolysis reaction ?? Wouldn't it be a hydration reaction?

Can someone please clarify

Thanks :))
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Yacoubb

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Re: VCE Chemistry Question Thread
« Reply #686 on: April 20, 2014, 07:11:50 pm »
+1
alkene + h20 ->

is the catalyst H+ or H3PO4?

And according to the text book, this is a hydrolysis reaction ?? Wouldn't it be a hydration reaction?

Can someone please clarify

Thanks :))

Reacting water with an alkene produces an alcohol. The catalyst is phosphoric acid, and this occcurs at 300oC.

Definitely not hydrolysis. This is an addition reaction.

Jawnle

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Re: VCE Chemistry Question Thread
« Reply #687 on: April 20, 2014, 07:26:24 pm »
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Reacting water with an alkene produces an alcohol. The catalyst is phosphoric acid, and this occcurs at 300oC.

Definitely not hydrolysis. This is an addition reaction.

I think an addition reaction contains subsets of other various reactions.
Because an addition reaction could be
- Hydrogenation (addition of hydrogen)
- Hydration (addition of water)
- Halogenation (addition of a group 7 atom)

I think Blondie21 is confused about how the water is being added , but it's not referred to as a hydration reaction. A hydrolysis reaction is breaking something by adding H20. So if you can see, both hydration and hydrolysis reactions contain water as their reactants.

That's just the way I see it haha, I'm not too sure myself

Yacoubb

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Re: VCE Chemistry Question Thread
« Reply #688 on: April 20, 2014, 07:32:52 pm »
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I think an addition reaction contains subsets of other various reactions.
Because an addition reaction could be
- Hydrogenation (addition of hydrogen)
- Hydration (addition of water)
- Halogenation (addition of a group 7 atom)

I think Blondie21 is confused about how the water is being added , but it's not referred to as a hydration reaction. A hydrolysis reaction is breaking something by adding H20. So if you can see, both hydration and hydrolysis reactions contain water as their reactants.

That's just the way I see it haha, I'm not too sure myself

Well hydrolysis is when water reacts with a compound to break an existing covalent bond so I can see why it would say its hydrolysis. But I reckon its more suitable to call thisba hydration reaction (addition).

Jawnle

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Re: VCE Chemistry Question Thread
« Reply #689 on: April 20, 2014, 07:44:58 pm »
+1
Well hydrolysis is when water reacts with a compound to break an existing covalent bond so I can see why it would say its hydrolysis. But I reckon its more suitable to call thisba hydration reaction (addition).

Yeah I agree it's more suitable to be called a hydration reaction (addition). Perhaps hydrolysis is more suited for esters and biochem you think?