Comments on: GCE ‘O’ Level Chemistry Final Leap Programme – Final Revision

By: hira

hira — Tue, 24 May 2011 16:44:45 +0000

thnx for encouraging

By: sean

sean — Wed, 05 May 2010 15:46:30 +0000

Thanks for the encouragement!

Hope you are doing well. Keep Learning!

By: SimpleChemConcepts | O Level Chemistry Examination - Kick Start in 18 Days time

Wed, 24 Feb 2010 17:07:27 +0000

[...] have been coaching several students under the FINAL LEAP PROGRAMME and i can see that many students are feeling the stress now. They are studying very hard (and [...]

By: Gracious

Gracious — Tue, 07 Oct 2008 15:00:03 +0000

I’ve indeed benefit from your blogs. Presently, am writing the ongoing GCE O’level. Am actually a Nigerian and am indeed grateful to you. Especially for owning a wonderful site like this and for being there to help people like us who see chemistry as a subject difficult to comprehend. I really don’t have much to say rather than praising you for a job well done. Though I still encounter difficulty in some areas. Thanks once again.

By: sean

sean — Tue, 30 Sep 2008 08:09:44 +0000

Hi Jennifer,

This question is testing you on your application of the basic concepts that you should have leanred in Organic Chemistry chapters.

The last two alkanes should be very very long. Personally i have only heard of this long chain why i was working with Dr. Wu Jishan from NUS-Dept of Chemistry. I read and understand that he has been researching on the many special properties of Pentacontane.

http://www.chemistry.nus.edu.sg/ourpeople/_files/Full%20Publications%20List-wu%20js.pdf

But you dont need all the tough chemistry to predict the boiling points of Pentacontane.

Based on the basic essential concepts that i have taught you in June’s Chemistry Intensive Revision Bootcamp, we know that boiling points are affected by the weak Van der Waals forces of attraction holding covalent molecules together.

Pentacontane is an alkane and thus a covalent molcule. For covalent molecules, the greater the chain length for molecule, the larger the amount of many weak Van der Waals forces acting between many molecules. As such, more heat energy is required to break the Van der Waals forces, before the molecules can break free and become gaseous. This means boiling points increases.

If question ask: “Why there is no boiling points for Pentacontane?”, then the answer must be around the fact that Pentacontane is a very long alkane molecule and they are too many Van der Waals forces acting between those molecules. This prevent the molecules to change from liquid state to gaseous state. Thus, no boiling points for Pentacontane.

PS: Pentacontane is a long alkane molecule made up of 50 Carbon atoms.

This applies to tetrachontane also.

Hope this explanation is useful to you!

To Your Academic Success in Chemistry,
Sean Chua
Master Trainer
http://www.SimpleChemConcepts.com