Wednesday, 1 May 2013

1.56 recall that one faraday represents one mole of electrons

One Faraday is 96500 coulombs. That is the amount of coulombs in one mole of electrons.

7 comments:

  1. I just noticed, it's 96500, not 95600

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    1. Oops :/ Thanks for pointing it out!

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  2. whatever it is,its value will be given in the question.

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  3. This comment has been removed by the author.

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  4. E.G (question 5 from paper 2C May 2012. KCHO/2C)

    Calculate the quantity of electricity, in coulombs, needed to produce 18 cm3 of chlorine gas. *( 1 Faraday= 96500 coulombs)

    Okay. LET'S DO IT. I'll do every single step (:
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    1) First we must find the number of moles in the 18 cm3 of chlorine gas.
    V=nmv ( volume= moles x molar volume)
    18cm3 = moles x 24000cm3 <--- same units!!
    rearrange it to get moles.

    18cm3/ 24000cm3 = moles = 0.00075

    2) Write down the half equation.

    2Cl' > Cl2 + 2e'

    3) Electricity always refers to "flow of electrons"

    2e' ( 2 electrons) are need to produce chlorine gas.

    2 electrons= 96500 x 2
    2 e'= 193000 C

    4) BUT what about the moles? just you wait...

    now times the number of coulombs by the amount of moles calculated in part 1)

    193000 x 0.00075= 144.75 Coulombs are need to produce 18 cm3 of chlorine gas.

    AND all done!! hope you understood and this helped (:

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