氯酸钠氧化性实验方法的探讨

Study of experiment method of sodium chlorate oxidbillity

氯酸盐是一种比较强的氧化剂,能与许多还原性物质发生反应,如与KI溶液反应即可将I-氧化成I_2单质,进一步氧化成IO_3^-.在氯酸钾氧化性实验中,学生往往观察不到单质I_2继续氧化成IO_3^-离子,观察不到正确的反应现象,甚至得出错误的结论.通过研究Na Cl O_3溶液和KI溶液的氧化还原反应,很容易观察到Na Cl O_3溶液和KI溶液的两步氧化还原反应,以及Na Cl O_3溶液的用量和溶液的酸碱度与Na Cl O_3溶液氧化性的关系.研究结果可知,在酸性环境下,0.50m L0.20mol·L^(-1)KI溶液加入0.20m L1.33mol·L^(-1)Na Cl O_3溶液就可以完成第一步反应;进一步加入0.10m L同浓度的Na Cl O_3溶液可完成第二步反应;若用0.50m L0.20mol·L^(-1)KI溶液与0.30m L1.33mol·L^(-1)Na Cl O_3溶液在不同酸碱度环境下反应,可得出完成两步反应溶液的最佳p H值应低于1.00.结果表明足量氯酸盐及强酸性环境是保证氯酸盐和碘化钾溶液两步氧化还原反应正常进行的必要条件.

Chlorate is a strong oxidant which is able to react with many reducing agents. When chlorate reacts with potassium iodide, iodine ion（I-） can be oxidized into free iodine and furthermore oxidized into iodate ion（IO3-）. During the oxidizing reaction of potassium chlorate and potassium iodide,IO3-is often observed instead of I2, which might lead to some wrong conclusions. By studying how the amount of Na Cl O3, KI and the reaction p H affects the oxidation of Na Cl O3, we found that under acid condition, the first reaction step can be achieved by mix of 0.50 m L 0.20mol·L（-1）KI and 0.20 m L1.33mol·L（-1）Na Cl O3, followed by addition of 0.10 m L 1.33 mol·L（-1）Na Cl O3 to complete the second reaction step. The best p H value of the two step reaction solution can be obtained if the 0.50 m L 0.20mol·L（-1）KI solution is reacted with the 0.30 m L1.33 mol ·L（-1）Na Cl O3 solution under different acidity conditions. The result showed： excessive amount of Na Cl O3 with an acid environment（p H 1.00） is necessary for the reaction steps of Na Cl O3 and KI, separately. Under such conditions, all the experiment phenomena are easy to observe.