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    Hi,

    I'm confused in this question why the mols at equilibrium = initial -
    change and not equilibrium mols = initial + change. I have obtained
    0.18 mols of N2 has reacted and 0.54 mols H2 correctly but the answer
    subtracts initial from change (mols that has reacted) can someone explain why thanks.
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    1 mol of N2 makes 2 mol of NH3.

    If you started with 10 mol of N2 and at equilibrium you find that you have 4 mol of NH3, then 2 mol of the N2 must have converted to NH3, i.e. you must have less N2 (8 mol remain).

    Why would you have more N2?
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    (Original post by Pigster)
    1 mol of N2 makes 2 mol of NH3.

    If you started with 10 mol of N2 and at equilibrium you find that you have 4 mol of NH3, then 2 mol of the N2 must have converted to NH3, i.e. you must have less N2 (8 mol remain).

    Why would you have more N2?
    Will this always be the case, will you have less mols at equilibrium than initially?
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    (Original post by Sloshy)
    Will this always be the case, will you have less mols at equilibrium than initially?
    Yes, you will always have less moles of reactants than initally (at equilibrium). And for the products you will always have more moles than initially (= 0 moles).

    If you think about it, initailly you only had reactants. At equilibirium you will have some products and this could only have happened if the reactants had reacted together to produce the products. (hence moles of reactants is lower than initially).

    Consider the graph below.
    Attached Images
     
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    (Original post by Sloshy)
    Will this always be the case, will you have less mols at equilibrium than initially?
    That depends on the Q.

    If there are only reactants at the start, then the reactants will go down, every time. But, if there are also products at the start (unusual, put possible) then the reactants could increase.
 
 
 
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