Rishi's Chemistry Thread

[nhmn0301]

A student performs two tests on an organic compound. In the first test, 3 mol of the compound was completely reacted with oxygen and 6 mol of carbon dioxide were produced. In the second test a few drops of bromine were added to the compound. The compound did not react rapidly with bromine. The formula of this compound is likely to be:
a) C₂H₄
b) C₂H₆
c) C₃H₈
d) C₆H₁₄
Pls show working out. Thanks

That would be B. So you have 3 ( C x H y ) produces 6 CO2. Hence you can say that 3x = 6 ( Carbon ), x = 2. We can eliminate C and D from now. Next, consider the fact that it DID NOT react rapidly with Bromine, which would be an alkane, since it is a saturated hydrocarbon, which has a formula C2H6.
Hope this helps!

[Rishi97]

That would be B. So you have 3 ( C x H y ) produces 6 CO2. Hence you can say that 3x = 6 ( Carbon ), x = 2. We can eliminate C and D from now. Next, consider the fact that it DID NOT react rapidly with Bromine, which would be an alkane, since it is a saturated hydrocarbon, which has a formula C2H6.
Hope this helps!

ohhhh that helps a lot I was just confused what bromine had to do with it but now it makes sense since it must be a alkane.
Thanks

[Rishi97]

Can I please have help with q 52 pg 61 of the checkpoints book? Sorry, it's got diagrams so I can't upload all of it.
I have identified that it can only be B or C but how do I calculate molecular mass of the bases?

Thanks

[Rishi97]

What is the name of the following compound ?

CH₃CH(CH₃)CO₂CH₂CH₃

Thanks

[lzxnl]

So...you have an ester, in which the alcohol used to make this ester is ethanol and it looks like it's reacted with 2-methylpropanoic acid.
Something like ethyl 2-methylpropanoate should be fine.

[Rishi97]

Describe the experiments you could carry out to distinguish between an alkane and an alkene. Include in your description any potential hazards and how they may be avoided.

Thanks

[lzxnl]

Describe the experiments you could carry out to distinguish between an alkane and an alkene. Include in your description any potential hazards and how they may be avoided.

Thanks

Easiest one is to place samples inside liquid bromine away from the light; the sample that decolourises bromine is an alkene.
Potential hazard? Well don't sniff any bromine vapours or let the liquid spill

[swagsxcboi]

Describe the experiments you could carry out to distinguish between an alkane and an alkene. Include in your description any potential hazards and how they may be avoided.

Thanks

Bromine (or Iodine) Test.
- Add a drop of Bromine (liquid at room temperature) into the test tube containing the sample
- Observe colour change; from orange to colourless (or pale orange) or orange remaining the same.
orange to colourless (or pale orange) means that an addition reaction has taken place between Br₂ and the alkene (unsaturated hydrocarbon)

orange remaining the same colour means that no reaction has taken place between Br₂ and the alkane (saturated hydrocarbon).

Iodine test is the same except for colour changes. Iodine turns purple to colourless, or remains purple.

Bromine and Iodine is harmful to the skin and eyes so gloves, apron and goggles are a must

[Rishi97]

Do we need to know what electrophoresis is and how it works?

[Yacoubb]

Do we need to know what electrophoresis is and how it works?

Nup all you need to know about DNA is about the primary and secondary structure of DNA.

[swagsxcboi]

Do we need to know what electrophoresis is and how it works?

You'll have to know it for bio later on 

[Yacoubb]

You'll have to know it for bio later on 

Dem Bio days! </3

[Rishi97]

Instructions for the production of a useful chemical, accompanied by appropriate safety warnings included
1. Take one litre of cooking oil, 3.5 grams of sodium hydroxide and 200mL of methanol.
2. Pour the methanol into a blender
3. Add 3.5g of sodium hydroxide and blend until the sodium hydroxide has completely dissolved.
4. Add the one litre of cooking oil and continue blending until the liquid seperates into two layers
The two layer referred to in this procedure would be:
a) a fatty acid and water
b) biodiesel and glycerol
c) an alcohol and a carboxylic acid
d) oil and water

I don't have the answer sorry but if you could also give a brief explanation of your answer, it would be great.
Thanks

[Rishi97]

Has anyone had their chem sac on organic chemistry yet?
If yes, what did you get tested on?
There's so much to remember and I don't know what's important and what I should study.
CHEM SAC TOMORROW!!!

[lzxnl]

Instructions for the production of a useful chemical, accompanied by appropriate safety warnings included
1. Take one litre of cooking oil, 3.5 grams of sodium hydroxide and 200mL of methanol.
2. Pour the methanol into a blender
3. Add 3.5g of sodium hydroxide and blend until the sodium hydroxide has completely dissolved.
4. Add the one litre of cooking oil and continue blending until the liquid seperates into two layers
The two layer referred to in this procedure would be:
a) a fatty acid and water
b) biodiesel and glycerol
c) an alcohol and a carboxylic acid
d) oil and water

I don't have the answer sorry but if you could also give a brief explanation of your answer, it would be great.
Thanks

Oil plus sodium hydroxide => fatty acid (well, conjugate base of fatty acid at least) + glycerol
Then plus methanol => methyl ester
You have biodiesel and glycerol as your two layers (one is non-polar, one is polar)

Has anyone had their chem sac on organic chemistry yet?
If yes, what did you get tested on?
There's so much to remember and I don't know what's important and what I should study.
CHEM SAC TOMORROW!!!

Each school's SACs will be different. Mine was on aspirin, spectroscopy, biomolecules, naming things and reaction pathways from memory. It wasn't a hard SAC but I completely messed up one of the IR questions (teacher put an amine in the SAC and I hadn't looked over what those absorptions looked like -.-)