# I don't understand this A-Level chem question

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#1
Hi, this question is based on entropy and I don't get why the answer is C. Could someone pls explain it? It's question 2.

https://pmt.physicsandmathstutor.com...e%204%20QP.pdf
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1 month ago
#2
Entropy is the disorder of particles. When the substances change state such as from liquid to aqueous, the disorder increases and so the entropy increases. In all the other equations the states change to be more rigid or packed together except for C. I hope this helps!
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1 month ago
#3
it's the only equation where there is a decrease in moles.
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#4
(Original post by gomc)
it's the only equation where there is a decrease in moles.
(Original post by itsprincess)
Entropy is the disorder of particles. When the substances change state such as from liquid to aqueous, the disorder increases and so the entropy increases. In all the other equations the states change to be more rigid or packed together except for C. I hope this helps!
I think I've either confused myself or have the wrong idea. For C, there's 6 moles of water and 5 moles of the aqueous ions together (because of the 4Cl and the Co2+) on the left hand side and on the right hand side there is again 6 moles of water and 5 moles of aqueous ions. Have I just misunderstood the question? I would appreciate any help!

My understanding is that there are equal moles of liquids and aqueous ions on each side of the equation. I'm pretty sure I'm wrong, could someone pls explain it?
Last edited by pineapple201; 1 month ago
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1 month ago
#5
(Original post by pineapple201)
I think I've either confused myself or have the wrong idea. For C, there's 6 moles of water and 5 moles of the aqueous ions together (because of the 4Cl and the Co2 ) on the left hand side and on the right hand side there is again 6 moles of water and 5 moles of aqueous ions. Have I just misunderstood the question? I would appreciate any help!

My understanding is that there are equal moles of liquids and aqueous ions on each side of the equation. I'm pretty sure I'm wrong, could someone pls explain it?
Liquid water has a certain amount of order due to the hydrogen bonding.
So for the first two equations it’s going from disordered aqueous solutions -> Aqueous solution and water(which is more ordered than an aqueous solution) therefore for the first two answers the entropy increases.
Disorder plus disorder ->disorder plus order

In C the equation starts off with water on the left hand side, so it is the opposite way around
Disorder plus order -> disorder plus disorder

So entropy decreases.
Last edited by GabiAbi84; 1 month ago
1
#6
(Original post by GabiAbi84)
Liquid water has a certain amount of order due to the hydrogen bonding.
So for the first two equations it’s going from disordered aqueous solutions -> Aqueous solution and water(which is more ordered than an aqueous solution) therefore for the first two answers the entropy increases.
Disorder plus disorder ->disorder plus order

In C the equation starts off with water on the left hand side, so it is the opposite way around
Disorder plus order -> disorder plus disorder

So entropy decreases.
Thank you so much for your reply! For the first 2 equations, would there not be an equal amount of disorder on the left and right hand side in terms of the water because even though water is a part of the aqueous solution, it's still a liquid? I'm really confused about this because since there is water on the RHS for both equations, I assumed that there was no increases in entropy, rather entropy remained the same due to same moles of water.

Sorry if I've confused you 0
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