(Solved) Calculate ∆H for the reaction :'(

fodog414

wrote...

Go to Answer

Posts: 279

Rep:

9 years ago

Calculate ∆H for the reaction

C6H4(OH)2(aq) + H2O2(aq) → C6H4O2(aq) + 2 H2O(l)

given the following data:

Equation     ∆H (kJ)
C6H4(OH)2(aq) → C6H4O2(aq) + H2(g)   177.4

H2(g) + O2(g) → H2O2(aq)     -191.2

H2(g) + ½ O2(g) → H2O(g)     -241.8

H2O(g) → H2O(l)     -48.8

∆H = kJ

I understand that you have to figure out the products and the reactants and flip the sign accordingly

I also get that you have to get rid of the fractions so Delta H would also be multiplied

But for some reason I keep missing up

With only one attempt left Frowning Face

Could anyone guide me?

Read 800 times

6 Replies

Report

Replies

Alexx

wrote...

Valued Member

On Hiatus

9 years ago

Hi,
Can you post the answers you tried so far? It doesn't seem terribly hard, you might did some miscalc or other mistake.

I'll also work with the exercise now and repost with my solution.

Report

Answer accepted by topic starter

Alexx

wrote...

Valued Member

On Hiatus

Related Topics

fodog414 Author

wrote...

9 years ago Edited: 9 years ago, fodog414

The computer randomizes to a different question when you get it wrong but I got 93.6

because wouldn't C6H4(OH)2(aq) → C6H4O2(aq) cancel each other out?

Leaving H202>> and 2H20 which means flip -191.2 to a positive form and keep H20 the same but times by 2?

so 191.2+2(-48.8)=93.6

Post Merge: 9 years ago

From what It looks like i think you are right i'll have to go over it again tomorrow to double check

But overall thank you!! Very clear and concise Slight Smile

Report

Alexx

wrote...

Valued Member

On Hiatus

9 years ago

Quote

because wouldn't C6H4(OH)2(aq) → C6H4O2(aq) cancel each other out?

Why should they cancel each other? They are two different molecules.

Quote

Leaving H202>> and 2H20 which means flip -191.2 to a positive form and keep H20 the same but times by 2?

There is no such reaction. The reaction you are looking is: H2O2(aq) → H2(g) + O2(g) which is different.

I think you are a bit confused?

Report

fodog414 Author

wrote...

9 years ago

What i was trying to get at was sense C6H4(OH)2(aq) → C6H4O2(aq)+H2 is the reaction shouldn't they be inversely proportioned to each other? Because wouldn't that mean that sense it takes 177. delta H kj to make C6H4(OH)2(aq) → C6H4O2(aq)+H2

It should also take -177.4 to produce C6H4O2(aq)+H2 → C6H4(OH)2(aq) ??

On the second part I understand that there is no such reaction but I was just focusing on the heat energy, because the other reactants and products are still there but H2=0 and from the above reasoning -177.4 +177.4 cancel each other out.

leaving H202 and 2H2O

Though from my earlier reply i'm pretty sure you are correct, I'll know for sure by Sunday Nerd Face

Report

fodog414 Author

wrote...

9 years ago

Thank you Alexx, I have a much stronger understanding now Slight Smile

Report

New Topic

Home Search Q & A Board Gallery Resource Library Blog Dictionary Chat	Quick Links Start a Topic Latest Topics Unanswered Questions Courses Study Tools Browse by Textbook	Social Facebook YouTube Community Stats Who's Online Trending Staff	Help About Us Take the Tour Study Tips Posting Guidelines Terms and Policies Contact Us
Biology Forums - Study Force © 2010-2024 \| Powered by SMF \| SMF © 2015, Simple Machines \| Sitemap Biology-Forums.com is not affiliated with any publisher. Book covers, title and author names appear for reference only.