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Concentration Help - AS

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    Would anyone be willing to answer some concentration questions on page 4 of the exam paper. I have answered all of them correctly except question e)v) the last part where it gets a bit confusing for me.

    http://www.scribd.com/doc/79256965?s...g7hqi4oynpdlvy
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    i) burette
    ii) n=conc x vol = 0.05 x (26.4/1000) = 1.32x10-3moles (remember to always divide cm3 by 1000 to get dm3)
    iii) 2:1 ratio so 6.6x10-4 moles H2SO4 in 20cm3
    iv) conc = mol/vol = 6.6x10-4 / (20/1000) = 0.033 moldm-3
    v) But this was a watered down sample from 10cm3 to 250cm3, so the original concentration was 25x more. so 0.825 moldm-3

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Updated: March 6, 2012
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