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Homework Help: A2 chemistry - how do i know there's an OH in the products?

  1. May 29, 2016 #1
    This is the question and the answer, the problem is i don't know how to get to the answer
    top is question and bottom is answer


    I attempted to divide the gas concentration by 24 to get molar mass, but that didn't work
    and how am i suppose to know that OH- is one of the products? i guessed that there is fe(OH)3, but that's all i got right....

    it's the very last question from this A level paper

    please help, my exams are close, and i have no clue at all....
  2. jcsd
  3. May 29, 2016 #2


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    Staff: Mentor

    I see no concentration in the question.

    And why do you divide? You have mass of 1 mL, right? Assuming there is one mole of a gas at RTP, what volume does it occupy? What is its mass (given the density as listed)?

    It is not that there is OH- between products, however, you won't be able to balance the reaction without either H+ of OH-. That's a quite common situation when it comes to redox reactions in water.
  4. May 29, 2016 #3


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    Homework Helper
    Gold Member

    1.3333 × 22 = very close to 32 so that part works well.
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