查看完整版本 : Kinetics of Acid-Catalyzed Iodination of Propanone

一隻小小雀 2012-11-30 07:49 PM

Kinetics of Acid-Catalyzed Iodination of Propanone

想問下呢個搵order of reaction的問題

我plot完第一幅圖 volume of na2s2o3 vs time 之後就知道I2 係zeroth order
跟住畫第二幅圖 slope of 1st graph vs vol. of propanone used 但係幅野畫左直線後條直線唔係from origin 係咪有問題嫁?? 咁問題 or error係d乜??

另外有條問題唔太識答 explain why pipette was used for measuring iodine solution whereas measuring cylinders were used for measuring propanone and sulphuric acid. 我知因為要KEEP I2個VOLUME constant所以一定要準so用pipette 咁另外果兩個用measuring cylinder 係咪唔需要太準求其d就得:smile_27: ??

請ching解答

jmlo 2012-12-1 05:42 AM

回覆 1# 的帖子

[quote] 我plot完第一幅圖 volume of na2s2o3 vs time 之後就知道I2 係zeroth order
跟住畫第二幅圖 slope of 1st graph vs vol. of propanone used 但係幅野畫左直線後條直線唔係from origin 係咪有問題嫁?? 咁問題 or error係d乜?? [/quote]
Note that the given reaction is zeroth order with respect to I2; therefore, the slope of the plot of [Na2S2O3] against time is a straight line. It means that the associated plot of d[Na2S2O3]/dt (i.e.., the slope of the first plot) against time for a given [propanone] is a horizontal line that does not pass through the origin unless the slope is absolutely zero. Therefore, your result makes complete sense.

[quote] 另外有條問題唔太識答 explain why pipette was used for measuring iodine solution whereas measuring cylinders were used for measuring propanone and sulphuric acid. 我知因為要KEEP I2個VOLUME constant所以一定要準so用pipette 咁另外果兩個用measuring cylinder 係咪唔需要太準求其d就得 ?? [/quote]
This is usually the case. Pipette is used when an accurate amount of solution is to be transferred. Also, for a transfer of a small constant volume of solution (e.g. 5, 10 or 20 ml), pipette is preferred. On the other hand, if accuracy is not a big concern or if a huge volume of solution (e.g. 500 ml or 1L) is to be transferred, a graduated cylinder is the choice.
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