Hey! Sign in to get help with your study questionsNew here? Join for free to post


Announcements Posted on
Last day to win £100 of Amazon vouchers - don't miss out! Take our quick survey to enter 24-10-2016
    • Thread Starter


    NaCl + H2SO4 --> NaHSO4 + HCL

    then why is,

    NaF + H2SO4 --> NaHSO4 + HF

    not right, why is it,

    2NaF + H2SO4 ---> Na2SO4 + 2HF


    For this you need to think about the relative bond enthalpies of HF and HCl. Sulfuric acid has two protons it can donate, however these two protons have different pKa's. In the top example, the first proton is donated, reacts with the chlorine ion in solution, forming HCl. The formation of the H-Cl bond releases enough energy to outweigh the energy needed to remove the proton from sulfuric acid. However, now you have HSO4-, meaning that it's going to be harder to remove the second proton as an already negative species isn't going to want to lose another positive charge. As a result, the formation of a second H-Cl bond does not release enough energy to outweigh the energy required to remove the second proton from HSO4-.

    For HF, the story is different. The H-F bond is much stronger than the H-Cl bond, so the energy released from the formation of the second HF is enough to outweigh the energy required to remove the second proton from HSO4-.

    Hope this helps.
Write a reply…


Submit reply


Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. Oops, you need to agree to our Ts&Cs to register
  2. Slide to join now Processing…

Updated: May 9, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

Would you rather find

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.