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Thread: Chem - salt problem AJ

  1. #1 Chem - salt problem AJ 
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    Hi, Can you help me on doing the steps to answer this problem?

    Given:
    Mass of Salt = 10 grams
    Total Volume = 1 litres
    --> the salt is dissolved into this volume to make a solution.
    pH of the Solution = 13.07
    --> salt is completely ionized in the solution.

    Required: Molecular Weight of the salt.

    Correct me: (given the mass; we need to find the number of mole)
    Step 1 - find concentration using the pH.
    pH = -log[A], where [A] is the concentration of the solution.
    Step 2 - find the number of moles is the solution.
    n (# of moles) = Volume (total volume) x Molarity (from step one)
    Step 3 - find the molecular weight by dividing the mass by the number of moles.
    MW (molecular weight) = mass divided by the # of moles.


    "Understanding is better than memorizing."
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  3. #2  
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    Hey, I got the correct steps and the right answer. Thanks anyways.


    "Understanding is better than memorizing."
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  4. #3 i agree 
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    Yeah, i totalyl agree with the understanding better than memorizing.

    The more you memorize, the more you forget and the more you will have a failuer in exam and wateva field.

    I used to memorize all the science subject last time instead of understanding. I had alomost spent all the time and i had been very tired of the science subjects.

    Pls...understand the subject before yuo really want to memorize it cos
    understand gain 75%, and memorizing only gain 25%

    understading + memorizing = 75% + 25%
    = 100%


    HAHAHA :wink:
    cheers
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  5. #4  
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    LOL. Thanks for your comment.

    Cheers!
    "Understanding is better than memorizing."
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  6. #5  
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    Just in case someone has a similar problem.

    The correction is in step 1. Since this is a basic solution, find the OH concentration (by using the fact that [H+][OH]=1x10^-14). Then apply this found concentration to the rest of the steps.

    "Understanding is better than memorizing."
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