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

AS Chemistry Rates of reaction

Announcements Posted on
Help us uncover the truth about exam cheats – is cheating ever ok? What if you wouldn't get caught? 27-06-2016
  1. Offline

    ReputationRep:
    I'm doing a past paper question on rates of reaction. It talks about a reaction between hydrochloric acid and magnesium carbonate, and asks what would be the effect on the rate of reaction if the acid was changed. But says assume the concentration of both acids is the same. I have no idea what the answer is. I would have said about different concentrations of the acids but that's obviously not correct. Help!
  2. Offline

    ReputationRep:
    (Original post by talliehughes)
    I'm doing a past paper question on rates of reaction. It talks about a reaction between hydrochloric acid and magnesium carbonate, and asks what would be the effect on the rate of reaction if the acid was changed. But says assume the concentration of both acids is the same. I have no idea what the answer is. I would have said about different concentrations of the acids but that's obviously not correct. Help!
    Does it say what acid it is changed to? It will more than likely be something to do with mole ratios.
  3. Offline

    ReputationRep:
    (Original post by talliehughes)
    I'm doing a past paper question on rates of reaction. It talks about a reaction between hydrochloric acid and magnesium carbonate, and asks what would be the effect on the rate of reaction if the acid was changed. But says assume the concentration of both acids is the same. I have no idea what the answer is. I would have said about different concentrations of the acids but that's obviously not correct. Help!
    It doesn't matter what acid is used.

    As long as the concentration of both are the same then we will have an equal no. of hydrogen ions reacting in the mixture.

    Hence, the rate will not change.

    EDIT: I strongly suggest reading the two posts after this one.
  4. Offline

    ReputationRep:
    (Original post by Ari Ben Canaan)
    It doesn't matter what acid is used.

    As long as the concentration of both are the same then we will have an equal no. of hydrogen ions reacting in the mixture.

    Hence, the rate will not change.
    What about a strong diprotic acid, e.g. H2SO4?
  5. Offline

    ReputationRep:
    (Original post by thegodofgod)
    What about a strong diprotic acid, e.g. H2SO4?
    The concentration is assumed to be the same.

    EDIT : I see where you are coming from.... I was thinking in terms of the concentration of H+ ions being the same. A diprotic acid of equal concentration as HCl would produce twice as many hydrogen ions and hence there would be double the no. of H+ ions.
  6. Offline

    ReputationRep:
    All it says is "replace with weak acid" that's why I would have mentioned about the concentration but then it says "assume the concentration of both acids and all other conditions are the same." I would have mentioned that the rate wouldn't change also but it asks us to sketch a curve on the graph next to the previous reaction with the hydrochloric acid. So I wasn't sure.
  7. Offline

    ReputationRep:
    (Original post by talliehughes)
    All it says is "replace with weak acid" that's why I would have mentioned about the concentration but then it says "assume the concentration of both acids and all other conditions are the same." I would have mentioned that the rate wouldn't change also but it asks us to sketch a curve on the graph next to the previous reaction with the hydrochloric acid. So I wasn't sure.
    If it's a weak acid then it doesn't undergo ionisation easily. Hence, there is likely to be a low concentration of H+ ions in the reaction mixture.

    Thus, the reaction rate falls.

Reply

Submit reply

Register

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 5, 2012
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.

Poll
Which way did you want the referendum to go?

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

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