VCE Chemistry Question Thread

[zhe0001]

How would an infra-red spectrum of butanoic acid differ from that of ethanoic acid?
Thanks!

[soNasty]

are we required to have knowledge of the principles of fractional distillation?

[gohfish]

are we required to have knowledge of the principles of fractional distillation?

Nope, as of the latest study design, fractional distillation is no longer part of the course

[Jason12]

are we required to name ethers and if so, how to name?

[Reus]

In what part of the electromagnetic spectrum does benzene absorb?
Explain why humans see benzene as colourless.

Thanks.

[Jason12]

Explain why humans see benzene as colourless.

probably because the wavelength of benzene is outside of the visible spectrum that humans can see so it is colourless.

Also how do you name hydrocarbons in this form?

CH3(CH2)2CH2NH2

[Yacoubb]

In what part of the electromagnetic spectrum does benzene absorb?
Explain why humans see benzene as colourless.

Thanks.

Because benzene absorbs wavelengths of light that are not in the visible spectrum of the electromagnetic spectrum. Thus, it appears colourless.

Also how do you name hydrocarbons in this form?

CH3(CH2)2CH2NH2

1-Butylamine.

[thushan]

Also how do you name hydrocarbons in this form?

CH3(CH2)2CH2NH2

butan-1-amine.

4 carbon compound => 'but'
no C=C double bonds => 'an'
an amino group in carbon 1 => '1-amine'

1-butylamine is an old name for that molecule, and would probably be penalised in the exam :/ - you need to use correct IUPAC terminology now.

[Yacoubb]

butan-1-amine.

4 carbon compound => 'but'
no C=C double bonds => 'an'
an amino group in carbon 1 => '1-amine'

1-butylamine is an old name for that molecule, and would probably be penalised in the exam :/ - you need to use correct IUPAC terminology now.

Thanks for that thushan. My teacher taught us the way I said, but you're right. Ugh now I have to adjust for the SAC and then the exam.

So for instance:

CH3(CH2)3CH2NH2

Would be

Pentan-1-amine??

[lzxnl]

are we required to name ethers and if so, how to name?

Nope, not needed for the exam
For simple ethers, there are two ways of naming them. Let's say you had CH3OCH3. You could call that dimethyl ether or methoxy methane. Similarly, CH3CH2OCH3 would be either ethyl methyl ether or methoxyethane, while CH3CH2CH2CH2OCH2CH3 would be butyl ethyl ether or ethoxybutane.

Thanks for that thushan. My teacher taught us the way I said, but you're right. Ugh now I have to adjust for the SAC and then the exam.

So for instance:

CH3(CH2)3CH2NH2

Would be

Pentan-1-amine??

Yes.

[Jason12]

thanks for the answers but I need to know what the brackets mean

e.g. (CH2)2 - is this saying a branch or just a chain of 2 more CH2 molecules

[lzxnl]

The brackets can mean two things. If I use them to write CH3CH(CH3)CH2CH3, for instance, it means the CH3 in brackets is a sidegroup.
If I use them to write CH3(CH2)10 CH3, that means there are 10 CH2s in a chain.

[soNasty]

It represents a chain of 2 or more CH2 molecules.
Lets just say you have Butan-1-amine, it has a structural isomer of 2-methyl-propan-1-amine, which can be represented as CH2CH(CH3)CH2NH2. Notice that when there is an -methyl or -ethyl group, there is a -CH before it.

EDIT: Beaten lol

[thushan]

Perfect.

[Jason12]

ok so how would an ethyl group be represented

if (CH2)2 means just 2 CH2 chains would ethyl be (CH2CH3)?