1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Neutralisation chemistry help

  1. Jun 7, 2006 #1
    can some one help me withe this?
    i want to neutralise a 400m3 of unknown solutions in pH 2 with sodium hydroxide. hw can i calculate the volume of alkaline needed? please help me!!!!!!!!!!!!!!!
     
  2. jcsd
  3. Jun 7, 2006 #2

    Hootenanny

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    HINT: Knowing the pH you can determine the hydrogen ion concentration.
     
  4. Jun 7, 2006 #3

    Borek

    User Avatar

    Staff: Mentor

    I hate such questions. You can't calculate anything without assuming that you have a solution of strong acid. Then (and only then) Hootenanny hint will work.
     
  5. Jun 7, 2006 #4
    Thank you

    Thank you! I solve it already by assuming it's a strong acid and got the answer. Thank you!
     
  6. Jun 8, 2006 #5

    Hootenanny

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Ahh, yes thank you Borek. I had forgotten about week acids (never liked them anyway :grumpy: ) As Borek said, I think one would have to assume that the acid in question is a strong acid as no dissociation constant is given.
     
  7. Jun 18, 2006 #6
    Problems Again

    I solved for the heat of neutralization already, I thought, but now, I got the final temperature after reaction is 121.75 oC which I think is too big.

    I start with initial pH = 2 and final the conc H+ = 10^-(pH=2) then I find the mole by multipling the conc with the tank volume (400m3), the I find the mass by multiply it with MW.

    To neutralise 1 mole of H+, I need 1 mole of OH-, so I balance the mole of OH- needed with the mole of H+ I calculated justnow. The I got the mass and volume of NaOH needed to neutralize the pH 2.

    The heat of neutralization is -55.9 kJ/mol. The energy balance is (m.Cp.del_T)in = (m.del_H) + (m.Cp.del_T)out

    But since i use the initial temperature and reference temperature both also 25 oC, so the (m.Cp.del_T)in is cancelled. What left is only
    -(m.del_H) = (m.Cp.del_T)out

    The part that confused me here is what m should I use for these m.del_H and m.Cp.del_T. I obtained the answer stated ealier (121.75 oC) by using the mass for m.del_H is the mass of water produced and the mass for m.Cp.del_H is the mass of the total mass of NaOH+H2SO4 that reacted. Is this correct? If yes, is the temperature I got reasonable? If not, whats my mistake?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Neutralisation chemistry help
  1. Chemistry help :] (Replies: 6)

  2. AS Chemistry help (Replies: 1)

  3. Chemistry help ! (Replies: 1)

  4. Chemistry Help! (Replies: 4)

Loading...