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    Determining percentage of copper in sample of brass,
    6g of brass was reacted completely with nitric acid.

    Resulting solution was neutralised and made up to 500cm^3 in a volumetric flask

    excess KI(aq) was added to 25cm^3 of this solution. iodine formed required 18.90cm3 of 0.200moldm3 Na2S2O3 for complete reaction/
    a mole of s2o32- is equivalent to one mole of cu2+

    determine percentage by mass of copper in sample of brass

    MY ANSWER

    n Na2S2O3 = 0.200*(18.90/1000)
    =0.00378 so 0.00378 n of Cu2_
    in 500cm3, = 0.0756

    mass = 0.0756 * 63.5
    4.80/6.00 = 80.0%
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    (Original post by ILoveUSA)
    Determining percentage of copper in sample of brass,
    6g of brass was reacted completely with nitric acid.

    Resulting solution was neutralised and made up to 500cm^3 in a volumetric flask

    excess KI(aq) was added to 25cm^3 of this solution. iodine formed required 18.90cm3 of 0.200moldm3 Na2S2O3 for complete reaction/
    a mole of s2o32- is equivalent to one mole of cu2+

    determine percentage by mass of copper in sample of brass

    MY ANSWER

    n Na2S2O3 = 0.200*(18.90/1000)
    =0.00378 so 0.00378 n of Cu2_
    in 500cm3, = 0.0756

    mass = 0.0756 * 63.5
    4.80/6.00 = 80.0%
    I've quickly done the calculation myself, and indeed you do have the correct answer
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    I believe it is


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    (Original post by ZakRob)
    I've quickly done the calculation myself, and indeed you do have the correct answer
    Woo! Thanks!
 
 
 
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