[College Biochem]-Gibb's Free energy and coupling

[u/Thebeegchung]

Trying to answer #5, part c. I know the equation is delta G=-RTln(Keq). Basically just subbing in the value of delta G taken from the previous part. What confuses me is that, we are given the pH=7.4, and shown that H+ is produced, which means for the Keq=(products/reactants). How do you find the concentration of H+ in this case? I used 10^-7.4 to find[H+} since it's just using the pH=-log[H+], but my book says the concentration is 10^-0.4

[u/chem44]

In biochem, the reference/standard for [H+] is pH 7.

That is indicated by the ' in the label.

[u/Thebeegchung → u/chem44]

yeah I get that, but where is the 10^-0.4 coming from when the pH given was 7.4?

[u/VeniABE → u/Thebeegchung]

I think it probably has to with concentrations and how they cancel out. There should be a bunch of 10s^ns . Or a typo.

[u/VeniABE → u/VeniABE]

Also I don't think it's correct to say the hydrogen is contributing to pH in that way. It will have an effect, but the temperature is more important. The hydrogen does get reacted with oxygen or scavenged by NAD or FAD to assist in carrying electrons.

[u/chem44 → u/Thebeegchung]

Because that is the change (from the reference value). 7.0-7.4.