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March 29, 2024, 06:16:40 am

Author Topic: VCE Chemistry Question Thread  (Read 2313355 times)  Share 

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soNasty

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Re: VCE Chemistry Question Thread
« Reply #600 on: April 14, 2014, 12:11:17 am »
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When converting an alkane to a carboxylic acid (eg ethane to ethanoic acid), why must we react it firstly with chlorine to form a chloroalkane(chloroethane), to then be reacted with h3po4 and oh- to form an alkanol(ethanol), to then be reacted with cr2o72- and h+ to form ethanoic acid?

cant we create ethanol from ethane in one reaction?

nhmn0301

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Re: VCE Chemistry Question Thread
« Reply #601 on: April 14, 2014, 04:36:44 am »
+2
When converting an alkane to a carboxylic acid (eg ethane to ethanoic acid), why must we react it firstly with chlorine to form a chloroalkane(chloroethane), to then be reacted with h3po4 and oh- to form an alkanol(ethanol), to then be reacted with cr2o72- and h+ to form ethanoic acid?

cant we create ethanol from ethane in one reaction?
Keep in mind that alkane is HIGHLY UNREACTIVE since it is a saturated hydrocarbon. Hence, there's really little chances for it to react with water to form alkanol like alkene does, the only way we can alter it is to use UV light to split the Cl2, forming a very high electronegativity ion that can attack and substitute one of the H+ on alkane. After that, we get a halo alkane, which can  undergo substitution reaction with NaOH for example to form alkanol, note that only then, the chlorine ion on the halo alkane creates a nucleophilic region (I.e possess a higher polarity degree) that the Cl- can be substituted with an OH-.
Hope this helps!
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soNasty

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Re: VCE Chemistry Question Thread
« Reply #602 on: April 14, 2014, 09:54:12 am »
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Thank you so much :)

Yacoubb

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Re: VCE Chemistry Question Thread
« Reply #603 on: April 14, 2014, 11:07:37 am »
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What questions does VCAA typically ask about DNA?

Rishi97

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Re: VCE Chemistry Question Thread
« Reply #604 on: April 14, 2014, 12:10:24 pm »
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Do we need to know the replication of DNA for chem? Its in ch 13 pg 209.
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Yacoubb

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Re: VCE Chemistry Question Thread
« Reply #605 on: April 14, 2014, 12:25:19 pm »
+1
Do we need to know the replication of DNA for chem? Its in ch 13 pg 209.

Nop!

Rishi97

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Re: VCE Chemistry Question Thread
« Reply #606 on: April 14, 2014, 02:51:20 pm »
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Nop!

So we need to know nothing about protein synthesis?
eg:
DNA unzips
mRNA strand is synthesized to match DNA triplet code
mRNA travels outside nucleus to ribosomes in cytoplasm of cell.
tRNA matching the mRNA brings amino acids together to make the protein chain.
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Rishi97

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Re: VCE Chemistry Question Thread
« Reply #607 on: April 14, 2014, 03:01:31 pm »
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Is the following statement important for vce?
- Two hydrogen bonds can form between the base pairs adenine and thymine. Three hydrogen bonds form betweem cytosine and guanine
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Yacoubb

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Re: VCE Chemistry Question Thread
« Reply #608 on: April 14, 2014, 03:08:18 pm »
+2
So we need to know nothing about protein synthesis?
eg:
DNA unzips
mRNA strand is synthesized to match DNA triplet code
mRNA travels outside nucleus to ribosomes in cytoplasm of cell.
tRNA matching the mRNA brings amino acids together to make the protein chain.


Nup

Is the following statement important for vce?
- Two hydrogen bonds can form between the base pairs adenine and thymine. Three hydrogen bonds form betweem cytosine and guanine


Yup!

Rishi97

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Re: VCE Chemistry Question Thread
« Reply #609 on: April 14, 2014, 04:53:48 pm »
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If ethanol is being made from chloroethane, can NaOH be used as a catalyst?
In the answers, it uses OH as the cataylst

Thanks
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Yacoubb

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Re: VCE Chemistry Question Thread
« Reply #610 on: April 14, 2014, 05:32:41 pm »
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If ethanol is being made from chloroethane, can NaOH be used as a catalyst?
In the answers, it uses OH as the cataylst

Thanks

You could use NaOH or KOH.

Rishi97

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Re: VCE Chemistry Question Thread
« Reply #611 on: April 14, 2014, 06:47:46 pm »
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You could use NaOH or KOH.

ok thanks. But is the OH binds with the alkyl group, where does the Na go? It's never included in any of the equations from the textbook
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vox nihili

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Re: VCE Chemistry Question Thread
« Reply #612 on: April 14, 2014, 07:10:14 pm »
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ok thanks. But is the OH binds with the alkyl group, where does the Na go? It's never included in any of the equations from the textbook

The Na just floats around, the OH too. Remember, they're aqueous.
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Rishi97

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Re: VCE Chemistry Question Thread
« Reply #613 on: April 14, 2014, 07:13:21 pm »
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The Na just floats around, the OH too. Remember, they're aqueous.

So we don't need to include Na in our equations?
Only if it asks for a balanced equation yeah
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nhmn0301

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Re: VCE Chemistry Question Thread
« Reply #614 on: April 14, 2014, 07:38:27 pm »
+1
So we don't need to include Na in our equations?
Only if it asks for a balanced equation yeah
What happens in that reaction is the Cl- possesses a very high electronegativity, hence, it will attract to the Na+ in the NaOH and create NaCl. The OH- now left alone will come into substituting the place of Cl- and bond with the partial positive Carbon
Hence, the whole equation is for e.g.:
CH3Cl(g) + NaOH (aq) -> CH3OH + NaCl (aq)
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