The pH of a solution is 2.57 at 25 degrees C. What is the molar concentration of hydronium ions? What is the molar concentration of hydroxide ions?

The pH of a solution is 2.57 at 25 degrees C.

What is the molar concentration of hydronium ions?
What is the molar concentration of hydroxide ions?

1 Answer
anor277
Sep 7, 2016

Given the definition of #pH#, I can write immediately that if #pH=2.57#, then #[H_3O^+]=10^(-2.57)# #mol*L^-1#

Explanation:

And also given the definitions, I know that #[H_3O^+][HO^-]=10^-14# under standard condtions; taking #log_10# of both sides, this gives our defining relationship:

#pH+pOH=14#

And thus #pOH# #=# #{14-2.57}#, and #HO^-# #=# #10^(-11.43)*mol*L^-1#.

Of course you will need a calculator to assess these values. I have never got one handy.

In a neutral solution at #298*K#, the equilibrium operates, #[H_3O^+][HO^-]=10^-14#, and #pH# #=# #pOH# #=# #7#. At temperatures higher than #298K#, how would you expect #pH# to evolve in a neutral solution. Would it increase, decrease, stay the same?

Related questions
See all questions in Molarity
Impact of this question
2606 views around the world
You can reuse this answer
Creative Commons License