0
$\begingroup$

I found an exercise in Physical Chemistry by Atkins et al, 8th edition, page 235 that I found confusing. The question is as follows.

"7.2(b) Molecular bromine is 24 per cent dissociated at 1600 K and 1.00 bar in the equilibrium Br2(g) ⇌ 2 Br(g). Calculate (a) K at 25°C, (b) ΔrG°, (c) K at 2000°C given that ΔrH° = +112 kJ.mol^(−1) over the temperature range."

I initially assumed that to answer (b), the temperature plugged to the equation ΔrG °= -RT.ln(K) is 298.15 K since it's mentioned that the reaction Gibbs energy is standard. However, when I checked my answer with the students' solutions manual, the author of the manual plugged in 1600 K as the temperature for the solution of (b). Who is correct and why? If the solutions manual author is the correct one here, why is there no agreement for a temperature in the context of "standard Gibbs energy?"

Thanks in advance for you who answer or inform if there has been any similar questions to mine in the forum since I haven't found one as I typed this.

Edit (last done on 9.51 PM UTC+7, 8th May 2022): @orthocresol has linked a question different from mine in the sense that what was asked circa 6 years ago was different than what I asked here; however, the answer to one of the linked questions is relevant to my question.

Improve this question
$\endgroup$
4
  • 1
    $\begingroup$ The standard state doesn't define a temperature; so there's no necessity for $\Delta_\mathrm{r}G^\circ$ to be at 298 K. (See also: What is the difference between ∆G and ∆G°?) I must say that the question wording is slightly confusing since that part is sandwiched between two different temperatures... $\endgroup$
    – orthocresol
    May 6, 2022 at 22:37
  • $\begingroup$ @orthocresol, I see. Thank you for providing some readings regarding the standard reaction Gibbs energy. $\endgroup$
    – Galen N. P.
    May 6, 2022 at 22:44
  • $\begingroup$ The question to the linked post is somewhat different but the answer is the same. $\endgroup$
    – Buck Thorn ♦
    May 7, 2022 at 5:45
  • 1
    $\begingroup$ Note that in specific context of electrochemistry, there is conventionally agreed the standard temperature 25 deg C. $\endgroup$
    – Poutnik
    May 7, 2022 at 17:26

0

Reset to default

Browse other questions tagged or ask your own question.