A Q in chemistry from BMAT 2006

Practice Question Solving
1

Hello

![WhatsApp Image 2023-08-30 at 21.52.50|690x350]
(upload://5VXG1dIvBYzO21BKSaVBx1Tmouz.jpeg)

BMAT 2006
Compound T has a melting point of 78°C and a boiling point of 134°C. T is soluble in water and its solution does not conduct electricity.
T has covalent bonding and has a simple molecular structure.
Which property of T is not usually associated with its bonding and structure?
A The melting point
B The boiling point
C The solubility in water
D The lack of conductivity of the solution

How Should I approach this Q? from what i understand ,the term “simple molecular structure” means VDW forces, with no molecular charge. In that case, why is it associated with conducting electricity?
:pray:

2

Hey, try reuploading the image

3

WhatsApp Image 2023-08-30 at 21.52.50
WhatsApp Image 2023-08-30 at 21.52.501024×520 47.5 KB

4

Hi! So the highlight of this question is that compound T is

  1. Covalently bonded and
  2. simply structured.

In case of

These two options indicate that T is covalently bond and simple, if you think about as more and more the compound gets complexly structured, it will be harder to break the bonds inbetween the molecules, therefore it gets harder to boil or melt it.

I think option D shows that T isn’t ionic compound cause ionic compounds like NaCl conducts electricity when they are in a state of aqueous solution.

Finally in this case, solubility in water can depend on many factors like hydrogen bonding, hydrophilic / hydrophobic characteristic, et cetera rather then covalent bonding or simple structure.

1 Like
5

thank you for answering.
From my understanding, solubility to water=hydrophilic=a polar molecule. is that a correct statement? if it is, can there be a simple molecular structure that do not conduct electricity but is soluble to water? or a simple molecular structure that conduct electricity but is not soluble in water?

6

That’s exactly what I thought when I was grading my paper the first time, and you are right about Soluble in water = polar molecule.

However, a compound could either be both polar and nonpolar, while simply structured + covalently bonded.

Example for the first case is HF (hydrogen fluoride), and the latter would be something like CCl4 (carbon tetrachloride).

Therefore, option C doesn’t really tell us anything :grinning:

1 Like
7

So if I understand correctly, H-F (aq) witch is not dissociated in its intramolecular bonds, but yes in its intermolecular bonds, does not conduct electricity.ON the contrary H+ (aq) & F-(aq) witch are completely dissolved do conduct electricity. Or in other words polar molecules don’t conduct electricity ions do. correct?