revisionlad
Badges: 14
Rep:
?
#1
Report Thread starter 2 years ago
#1
Hi, was wondering why Strong Acid + Strong Base reactions are generally more exothermic than Weak Acid + Weak base reactions?

Thanking you.
0
reply
MushiRock11
Badges: 13
Rep:
?
#2
Report 2 years ago
#2
(Original post by revisionlad)
Hi, was wondering why Strong Acid + Strong Base reactions are generally more exothermic than Weak Acid + Weak base reactions?

Thanking you.
Strong Acid + Strong Base gives you a more exothermic reaction because the Acid loses its protons/H+ ion more readily while the Base accepts it more readily. Hence, it’s an irreversible reaction and the rate of reaction is faster.
On the other hand, a Weak Acid + Weak Base is a reversible reaction and the Acid partially loses its proton while the Base partially accepts it.

I hope this is crystal clear for you but if not, feel free to ask more Qs.
0
reply
revisionlad
Badges: 14
Rep:
?
#3
Report Thread starter 2 years ago
#3
(Original post by MushiRock11)
Strong Acid + Strong Base gives you a more exothermic reaction because the Acid loses its protons/H+ ion more readily while the Base accepts it more readily. Hence, it’s an irreversible reaction and the rate of reaction is faster.
On the other hand, a Weak Acid + Weak Base is a reversible reaction and the Acid partially loses its proton while the Base partially accepts it.

I hope this is crystal clear for you but if not, feel free to ask more Qs.
Hey. Thanks for the answer.

1. I understand what you mean about the dissociation aspect, but how does this affect the Thermodynamics of the reaction exactly, perhaps would it affect how bonds form? i.e. on my Scheme of Work (supplement to my Spec it says '

"Explain the exothermic nature of sodium hydroxide with hydrochloric compared to ammonia with ethanoic acid" - - - -

So is there anything to do with the thermodynamics of the Bonds being broken/formed in this case?


2. This leads me onto the next q, about how I didn't really understand how you corellated reaction rate into this? Can u explain why an irreversible reaction can have higher reaction rate?

Thanks again!
0
reply
MushiRock11
Badges: 13
Rep:
?
#4
Report 2 years ago
#4
(Original post by revisionlad)
Hey. Thanks for the answer.

1. I understand what you mean about the dissociation aspect, but how does this affect the Thermodynamics of the reaction exactly, perhaps would it affect how bonds form? i.e. on my Scheme of Work (supplement to my Spec it says '

"Explain the exothermic nature of sodium hydroxide with hydrochloric compared to ammonia with ethanoic acid" - - - -

So is there anything to do with the thermodynamics of the Bonds being broken/formed in this case?


2. This leads me onto the next q, about how I didn't really understand how you corellated reaction rate into this? Can u explain why an irreversible reaction can have higher reaction rate?

Thanks again!
I’m sorry, I haven’t learned the neutralisation reaction in terms of the thermodynamics involved. All I can think of is that the Acids and Bases ionise more easily and so bond formation and bond breaking requires lesser energy and hence is more exothermic as reaction is more explosive than the reversible reactions.

About the reaction rate, I really ought to have elaborated on it. Sorry for that! What I meant was for Reversible reactions, the equilibrium may shift to both sides depending on the sorroundings, as stated by the Le Chatelier’s Principle. However, for Irreversible reactions, it will always proceed to the Product side even if there are more products and lesser reactants. I think reaction rate is the wrong term to use here and so do pardon me. It’s the yield that matters.
1
reply
username3249896
Badges: 12
Rep:
?
#5
Report 2 years ago
#5
(Original post by revisionlad)
Hi, was wondering why Strong Acid + Strong Base reactions are generally more exothermic than Weak Acid + Weak base reactions?

Thanking you.
For eg, HNO3 + NaOH is more exothermic than CH3COOH + NaOH.

In the 2nd case, the CH3COOH dissociates:

CH3COOH <--> CH3COO- + H+

As more H+ reacts, according to Le Chatelier's, the equilibrium shifts to the right and more H+ is formed. Eventually all the acid molecules have ionised and all H+ has reacted.

However, some energy must be taken in to ionise the acid. Breaking the O-H bond is endothermic.
1
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Should 'Mental health support' be included on league tables?

Yes (215)
74.91%
No (72)
25.09%

Watched Threads

View All