Cramster.com - Homework Solutions, Lecture Notes, Exams, and Free Online Homework Help
Sign Up Now! Login Customer Support Cramster Blog
McAfee Secure sites help keep you safe from identity theft, credit card fraud, spyware, spam, viruses and online scams
Problem Solved.
    Home    
    Homework Help    
   Answer Board   
    Resources (Beta)    
   
You Are Here: Home > Answer Board > Chemistry > Topic: enthaply 4
Member's Topic Headline:

enthaply 4

Know the answer? Have a better solution? Share it.
Sign Up Now for FREE!
Join the thousands of students
getting ahead in their classes.
Member Testimonials

Question:

Advertisement:
Answer | Ask New Question | Customize Profile | Leaderboards | 
FAQ

Member's Avatar
Scholar
Karma Points: 200
Respect (85%):
Date Posted: 7/23/2008 10:19:50 PM  Status: Live
enthaply 4
Course Textbook Chapter Problem
N/A N/A N/A N/A
Question Details:
Since most chemical reactions are conducted in containers open to the atmosphere, why is the heat of chemical reaction generally expressed as teh change in enthalpy?
Bonus Point Alert! Earn +4 additional karma points for helping this annual member.

Answers:

Member's Avatar
Sage
Karma Points: 4,913
Date Posted: 7/24/2008 1:51:52 AM  Status: Live
Asker's Rating: Helpful   
Response:
So, this implies constant pressure. I think, but I am not sure, that this has implications that none of the heat is diverted to other forms, such as work

dH = dQ-VdP

At constant pressure, no shaft work occurs,

so dH = dQ, where Q is heat transferred.
Please PM me if you have more questions and don't forget to rate my answer.

Member's Avatar
Guru
Karma Points: 1,798
Date Posted: 7/24/2008 4:49:29 AM  Status: Live
Asker's Rating: Helpful   
Response:
 In vitro (i.e) under lab conditions we should make any of the three conditions(temperature ,pressure, volume ) are made constant to know the other two properties .so under vivo conditions pressure is made constant i.e room conditions (1 atmosphereric pressure).
 Change in entrophy gives the energy requires for a reaction to become spontaneous.  

Member's Avatar
Guru
Karma Points: 1,773
Date Posted: 7/24/2008 8:35:01 AM  Status: Live
Asker's Rating: Lifesaver   
Response:
Experiment can be conducted by two methods i.e open vessel and closed vessel
  In open vessel pressure is constant and the system is allowed to expand, i.e the given heat  is utilized in two ways, it increases the internal  energy as well work is done in doing work
  Heat supplied = ΔE + W
      ΔE is the change in internal energy and W is the work done
                       W = PΔV
 Generally reactions are carried in closed vessel because the reaction cannot proceed in back ward direction
 
When carried in closed vessel the given heat energy is utilized for only increasing internal energy
The change in volume is zero because the gases are not allowed to expand



By reading or posting messages on these forums, you are agreeing to the Answer Board's Terms of Service and Conduct (TSC).


About Cramster | Terms of Use | Privacy Policy | Contact Us | Press Room | Site Map | Support | Anti-Cheating Policy

Cramster.com is not affiliated with any publisher. Book covers, title and author names appear for reference only.
Copyright © 2008 Cramster, Inc.