Explanation to Acid Base

[matt123]

Yea we're saying B for q 14 but A for q 15

D, H's are being used up.

Unfortunately that's not correct.
The fuel cell uses an alkaline electrolyte. At the cathode, even more hydroxides are bring produced. The pH rises due to this accumulation.

B is correct.

I clarify my statement: if you add hydroxides to acid, the pH rises because you are removing acid by a reaction. If you add hydroxides to base, there isn't much H+ yo react with, and the pH rise is due to accumulation of hydroxide

Mao must've gotten confused between the two questions cause he said "The pH rises due to this accumulation [of OH-]" then said B (pH decreases as OH is used up) is correct.

yeh agreed

[kenhung123]

I was thinking of it in terms of the ionisation of water, as [OH-] increase, the reaction shifts to produce more water H+'s are confused and pH increases!

[kenhung123]

Why does diluting strong acid increase pH when the reaction is HCl + H2O => H3O+ + Cl-?

[Whatlol]

Why does diluting strong acid increase pH when the reaction is HCl + H2O => H3O+ + Cl-?

Concentration of H30+ will fall when you dilute...

[matt123]

Why does diluting strong acid increase pH when the reaction is HCl + H2O => H3O+ + Cl-?

Concentration of H30+ will fall when you dilute...

NO UR WRONG. its because CHEMISTRY IS MAGICAL!..


nah hes  right

i mean .. think of it.
if you have a strong concentrated acid .. and u put water in it .. guess what happens .. it becomes LESS concentrated

its the same thing here ... add water .. = less concentration of H30+ .. meaning B00M HIGHER PH.

[Blakhitman]

Diluting increases volume, c=n/v v increases so c decreases.

No magic here 

[kenhung123]

Lol I was thinking in terms of equilibrium and shifting concentrations. Thanks for the clarification

[matt123]

Lol I was thinking in terms of equilibrium and shifting concentrations. Thanks for the clarification

No , thank you

[98.40_for_sure]

Why does diluting strong acid increase pH when the reaction is HCl + H2O => H3O+ + Cl-?

I think the question he is trying to ask here has to do with physical change vs. chemical change. The point he's making is that adding water leads to a forward reaction as 1 particle vs. 2 particles, it will shift to the side with more dissolved particles to increase the overall concentration, thus increases the conc. of H+, which in turn decreases pH. However, the initial diluting cannot be fully compensated for through the system returning to equilibrium, thus overall conc of H+ decreases, and pH will increases.

[Mao]

Why does diluting strong acid increase pH when the reaction is HCl + H2O => H3O+ + Cl-?

Remember LCP?

Dilution will decrease concentration of all species. Even though the subsequent change is to produce more H+, this will only be partial, and [H+] invariably drops.

Another point is strong acids do not behave as if they are in equilibrium, because they are so damn strong you get 99.9999999999999999999999999999999999% conversion, the equilibrium lies all the way to the right by about twenty million billion miles. Thus when you dilute, there is no subsequent change, you just get diluted.

Weak acids tend to bounce back a little, but LCP, the pH still rises.

Also, apologies for the previous confusion. You are right in that I was confused, A is the correct answer.

[kenhung123]

Great. I understand now. Thanks.

[kenhung123]

For a solution that contains involved this reaction:
If I add water, the equilibrium position shifts forward and more OH- produced but still [OH-] is lower. Would you say the pH decrease because [OH-] is lower or because [H+] is higher?

I am not sure if this is considered an alkaline environment or neutral.