How do I calculate the Gibbs free energy change for a reaction when given the entropy change, enthalpy change and the reaction conditions>

deltaG= Gibbs free energy 

deltaG=deltaH - TdeltaS 

If deltaH= 150 kJ/mol and deltaS=2.1 J/mol we must first convert the deltaS into kJ/mol, this is done by multiplying by 10-3 .

So deltaS= 2.1 x 10-3 kJ/mol. If the reaction is done at 25 degrees celcius, we must convert it to Kelvin, by adding 273. This gives 298 K. 


So the value of deltaG can be worked out:


deltaG= (150 kJ/mol) - (298) x( 2.1x 10-3

deltaG= 149. 4 kJ/mol 


Archit M. GCSE Chemistry tutor, A Level Chemistry tutor, A Level Exte...

2 years ago

Answered by Archit, an A Level Chemistry tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist


£20 /hr

Devajit D.

Degree: Medicine (Bachelors) - University College London University

Subjects offered:Chemistry, Biology+ 2 more

-Personal Statements-
-Medical School Preparation-

“Who am I? My name is Devajit Das, but you can call me Dev. I’m currently a first year medical student at UCL, having studied biology, chemistry and business studies at A-level. I’ve always been curious of these sciences and I hope I c...”

£20 /hr

Laura B.

Degree: Chemistry (Bachelors) - York University

Subjects offered:Chemistry, Russian+ 2 more

-Personal Statements-

“Hello! My name is Laura and I am very passionate about science! I am currently studying Chemistry with Biological and Medicinal Chemistry at University of York and I really hope that my passion about science will inspire you!  I am ve...”

£22 /hr

Henry P.

Degree: MChem Chemistry with a Year in Industry (Masters) - Cardiff University

Subjects offered:Chemistry, Physics+ 2 more

-Personal Statements-

“About Me: I am studying Chemistry at Cardiff University and am now in my second year having passed with a first in all my modules last year. I really love all things science and have a real drive to pass on what I know to other people....”

About the author

Archit M. GCSE Chemistry tutor, A Level Chemistry tutor, A Level Exte...

Archit M.

Currently unavailable: for regular students

Degree: Chemistry (Masters) - Manchester University

Subjects offered:Chemistry, Maths+ 1 more

Extended Project Qualification

“4th Year Chemist. University of Manchester. Generally knowledgeable about Science. I also like working on improving personal statements, CVs and helping with Interview practice- I've had plenty! ”

You may also like...

Other A Level Chemistry questions

Describe how you test for an aldehyde or ketone and distinguish between the two.

Dehydration reaction involving ethanol will produce ....

What is an isomer?

How do you calculate the pH of a weak acid?

View A Level Chemistry tutors

We use cookies to improve your site experience. By continuing to use this website, we'll assume that you're OK with this. Dismiss