Chem計數一問急!

2013-06-07 5:23 am

It is back titration+dilution factor:
6.7cm3 of household bleach solution which contain NaOCl as an active ingredient was diluted to 250cm3 ,
25cm3 of the diluted bleach solution is completely reacted with 10cm3 1M Kl(aq) and 10cm3 2M H2SO4.(Kl and H2SO4 is excess)
NaOCl + 2Kl +H2SO4 to form I2 +NaCl +H20 +K2SO4
The iodine given out is completely reacted with 15cm3 of 0.05M Na2S2O3.
l2+2NA2S2O3 to form 2Nal +Na2S4O6
calculate the molarity of NaOCl in the household bleach solution,

更新1:

10cm3 1M Kl(aq) and 10cm3 2M H2SO4.(Kl and H2SO4 is excess)呢D資料冇用?

回答 (1)

胡雪8°

2013-06-07 7:08 am

✔ 最佳答案

Consider the titration of Na2S2O3against the I2 formed:
I2 + 2Na2S2O3 → 2NaI + Na2S4O6
No. of moles of Na2S2O3 used = 0.05 x(15/1000) = 0.00075 mol
No. of moles of I2 formed = 0.00075 x (1/2) = 0.000375 mol

Consider the reaction of the diluted bleach solution to form I2:
NaOCl + 2KI + H2SO4 → I2 + NaCl + H2O+ K2SO4
No. of moles I2 formed = 0.000375 mol
No. of moles of NaOCl in 25 cm³ of diluted bleach = 0.000375 mol

No. of moles of NaOCl in household bleach = 0.000375 x (250/25) = 0.00375 mol
Molarity of NaOCl in household bleach = 0.00375 / (6.7/1000) = 0.560 M

2013-06-07 17:57:24 補充：
10cm3 1M Kl(aq) and 10cm3 2M H2SO4.(Kl and H2SO4 is excess)呢D資料冇用?

有用的資料是："in excess"。所以保證 complete reaction，但計算時不用這些數據。

2013-06-07 17:57:33 補充：
10cm3 1M Kl(aq) and 10cm3 2M H2SO4.(Kl and H2SO4 is excess)呢D資料冇用?

有用的資料是："in excess"。所以保證 complete reaction，但計算時不用這些數據。

參考: 胡雪, 胡雪

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Chem計數一問急!