Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Help with calculating the headspace concentration of butyric acid in a 1 mM

Help with calculating the headspace concentration of butyric acid in a 1 mM

Help with calculating the headspace concentration of butyric acid in a 1 mM

Hi everyone,

I´m stucked with a very easy chemistry problem. I have a 10ml crimped vial with 2ml of a 10 mM solution of butyric acid, the headspace volume is 8 ml. Our company is developing a sensor and we need to know the concentration of butyric acid in the headspace of the closed vial.

I´ve tried to make the calculation with the following formula:

n=Pg x Vh/R x T

Where Pg is the partial pressure of butyric acid in the headspace and Vh is the volume of the headspace.

I obtained Pg from the following formula: Pg=Ca/Kh, where Ca is the concentration of butyric acid in aqueous solution and Kh is the henry´s law constant for butyric acid (1900 M/atm).

n= (2.63x10-5)x(0.008L)/0.08205 atm L mol-1 K-1 x 293 K
n=8.75x10-9 mol

To get the concentration in the headspace I divide the mols I obtained above by the headspace volume (0.008L). I get a headspace concentration of 0.00109mM.

This seems extremely low to me, and I have the feeling that there is a mistake in the way I´m making the calculations, but I can´t put my finger on it.

I would really appreciate if somebody out there could give me a hand with this. Thanks so much in advance.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


White Paper - A Guide to 3D Printing Materials
When it comes to using an FDM 3D printer effectively and efficiently, choosing the right material at the right time is essential. This 3D Printing Materials Guide will help give you and your team a basic understanding of some FDM 3D printing polymers and composites, their strengths and weaknesses, and when to use them. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close