January 24, 2022, 05:23:40 AM
Forum Rules: Read This Before Posting


Topic: Help with an exercise pH  (Read 421 times)

0 Members and 1 Guest are viewing this topic.

Offline Kirtha

  • Very New Member
  • *
  • Posts: 2
  • Mole Snacks: +0/-0
Help with an exercise pH
« on: December 18, 2021, 03:42:23 PM »
Hi, I have been trying to solve this exercise:

Check that the pH of these two solutions for a concentration of 0.01M is 4.6 and 9.6. Givens: H2P04 pka1=2.15, pka2=7.2 and pka3=12.4


I managed to prove that the 1st pH is 4.6 but I have no clue how to get the 9.6 one? Is this something anyone can help me to understand how to do it?

Thanks!

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 26925
  • Mole Snacks: +1746/-403
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Help with an exercise pH
« Reply #1 on: December 18, 2021, 03:57:33 PM »
I don't see two solutions.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline Kirtha

  • Very New Member
  • *
  • Posts: 2
  • Mole Snacks: +0/-0
Re: Help with an exercise pH
« Reply #2 on: December 18, 2021, 04:10:35 PM »
Yeah, that confuses me too. But unfortunately. that is everything what the problem provides.

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 26925
  • Mole Snacks: +1746/-403
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Help with an exercise pH
« Reply #3 on: December 18, 2021, 07:07:22 PM »
If so, question doesn't make sense.

Also, pH of 4.6 for a 0.01M solution of phosphoric acid (assuming that's what the question intends to ask) is over two units off.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline Babcock_Hall

  • Chemist
  • Sr. Member
  • *
  • Posts: 5078
  • Mole Snacks: +295/-22
Re: Help with an exercise pH
« Reply #4 on: December 20, 2021, 08:29:47 AM »
I have not checked the numbers (busy morning for me), but 4.6 sounds in the right ballpark for a solution of the mono-anion, H2PO41-.
« Last Edit: December 20, 2021, 08:48:41 AM by Babcock_Hall »

Sponsored Links