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投影实验一“氢碘酸的电解”(以下简称实验,刊于1982年2期《化学教育》),用0.2molL~(-1)的 Kl 和0.5molL~(-1)的 H_2SO_4配制HI 溶液,以带锈铁棒为阳极,石墨为阴极,在电压为1～3 V 时进行电解,其电极反应为:阳极 2I~-→I_2+2e阴极 2H_2O+2e→2OH~-+H_2《实验》认为:“利用投影装置,可以很清楚地看到阳极上析出碘晶体和阴极上产生氢气泡”。我们按实验所述条件,并扩大酸度和电压范围反复进行实验,结果得不到碘晶体。根据我们多次的实验情况,对这个问题分析如下:《实验》对两极距离未加说明,我们用 U形管做电解槽(两极间距离约15cm),电解
Projection experiment 1 “electrolysis of hydroiodic acid” (hereinafter abbreviated as experiment, published in the 2nd issue of “Chemical Education” in 1982), HI solution was prepared with 0.2 mol L -1 Kl and 0.5 mol L -1 H_2SO_4. With rusted iron rods as anodes and graphite as cathodes, electrolysis is performed at a voltage of 1 to 3 V. The electrode reactions are as follows: Anode 2I~-→I_2+2e cathode 2H_2O+2e→2OH~-+H_2 “Experiment” It is thought that “Utilizing a projection device, we can clearly see the precipitation of iodine crystals on the anode and hydrogen bubbles on the cathode.” We repeated the experiment according to the conditions described in the experiment and extended the acidity and voltage range. As a result, iodine crystals could not be obtained. According to our many experiments, we analyze this problem as follows: “Experiment” does not explain the distance between two poles. We use U-shaped tubes as electrolyzers (distance between two poles is about 15cm), electrolysis.