The Student Room Group

Can anyone explain this Chem4 AQA exam question?

Hello!

I just wrote out the answer to this question from answer sheet and uploaded a photo with this question. Can anyone explain the theory behind this question? I have never learned this nor does my textbook teach it!!
I really hate when this happens. I have never seen the benzene without its ring and don't know any theory as to what and why!
Please help!!!


2015-02-28 21.23.39.jpg512.4KB
It seems to be benzene being hydrogenated to cycloalkane by the addition of 3 H2. Hydrogenation uses a nickel or platinum catalyst. Generally, the addition of H tends to be considered reduction, if you're wondering about why reduction = hydrogenation. As for the bond angles: for cyclohexane, each carbon atom is bonded to two other carbons and two hydrogen. This gives a tetrahedral angle (109.5). For benzene, each carbon atom is bonded to two carbons and one hydrogen, giving a trigonal planar angle (120). Also, if you're wondering about how I knew that the structure shown was cyclohexane, you should look up skeletal formulae.

Hope this helps :smile:
(edited 9 years ago)
Thank you for the reply!! I am just doing some mocks over the weekend and I am a little disheartened I can't seem to push past around 80% or between 100 and 104 UMS on average. My problem is I need around 115 UMS on each of the papers to get an A* or else due to my B grade and points at AS I will achieve a B, no in between!!
How are you doing?

Original post by HenryHiddler
It seems to be benzene being hydrogenated to cycloalkane by the addition of 3 H2. Hydrogenation uses a nickel or platinum catalyst. I haven't a clue about the bond angles.

Hope this helps :smile:
Original post by Hexaneandheels
Thank you for the reply!! I am just doing some mocks over the weekend and I am a little disheartened I can't seem to push past around 80% or between 100 and 104 UMS on average. My problem is I need around 115 UMS on each of the papers to get an A* or else due to my B grade and points at AS I will achieve a B, no in between!!
How are you doing?

Have you tried the UMS converters after marking? Or are you guessing at the UMS? I haven't started past papers myself, as I'm focusing on Unit 5, which I find to be the harder of the two, especially where you have to remember the colours for like 15 complex ions :/
I've got an explanation for the bond angles - check my edit.

Hope this helps :smile:
(edited 9 years ago)
Hi yes I am using the UMS converter tool and so far these are my averages.

I know exactly how you feel for Chem 5 but in a way I prefer it to Chem 4,
I a averaging between 90 and 104 UMS on that paper too! Attempted about three so far. Stupid mistakes every time, otherwise they would be around 115 UMS. I just hope they can be pulled up and I haven't hit a block.
For the complexes I did make a silly little way to remember the complexes, just make a funny rhyme that includes the letters of the complex and the solution colour.
I have most trouble with the catalyst stuff, Cr2+ etc, I keep forgetting that stuff.
Definitely a lot to do and don't even get me started on the disaster that is Physics!!!! Needing the same sort of grades in that as well, same situation!!

Original post by HenryHiddler
Have you tried the UMS converters after marking? Or are you guessing at the UMS? I haven't started past papers myself, as I'm focusing on Unit 5, which I find to be the harder of the two, especially where you have to remember the colours for like 15 complex ions :/
I've got an explanation for the bond angles - check my edit.
Thank you just checked your edited post you have helped a lot!

Original post by HenryHiddler
Have you tried the UMS converters after marking? Or are you guessing at the UMS? I haven't started past papers myself, as I'm focusing on Unit 5, which I find to be the harder of the two, especially where you have to remember the colours for like 15 complex ions :/
I've got an explanation for the bond angles - check my edit.
Original post by Hexaneandheels
Hi yes I am using the UMS converter tool and so far these are my averages.

I know exactly how you feel for Chem 5 but in a way I prefer it to Chem 4,
I a averaging between 90 and 104 UMS on that paper too! Attempted about three so far. Stupid mistakes every time, otherwise they would be around 115 UMS. I just hope they can be pulled up and I haven't hit a block.
For the complexes I did make a silly little way to remember the complexes, just make a funny rhyme that includes the letters of the complex and the solution colour.
I have most trouble with the catalyst stuff, Cr2+ etc, I keep forgetting that stuff.
Definitely a lot to do and don't even get me started on the disaster that is Physics!!!! Needing the same sort of grades in that as well, same situation!!

Fair enough haha :P We've also had some *ahem* teaching problems for physics, so that's another thing to contend with :/

Hope this helps :smile:
(edited 9 years ago)

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you