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Chemistry unit 1 june 2014 lattice energy question Watch

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    I am supposed to use these values to find the value of G . When I get to write my equation I use the concept of vectors and add the ones in same direction and subtract the opposite ones . In the markscheme , the sum of electron affinity values are added up this way , ( -141 +790) but they r in opposite directions to each other shouldn't it be ( 790 -(-141)) or (-141-790) ??
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    Going from the top left (2Na+ + O + 2e-) to the stage after A involves going in the direction of the arrow, i.e. adding the value corresponding to A

    i.e you add A

    and then add B

    -> + (-141) + (+790)
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    (Original post by Pigster)
    Going from the top left (2Na+ + O + 2e-) to the stage after A involves going in the direction of the arrow, i.e. adding the value corresponding to A

    i.e you add A

    and then add B

    -> + (-141) + (+790)
    Thanks alot
 
 
 
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