✔ 最佳答案
Sodium hydroxide in solid or solution cannot give out heat. Only when we add water to it, the dilution will be exothermic so that heat will be given out. We cannot prepare sodium hydroxide solution already to expect it keeps on giving out heat because the exothermic reaction will end before we use it. On the other hand, we mustn't add water to solid sodium hydroxide to provide heat. Because it is highly corrosive and if you put in a plastic holder, it will corrode plastic too. So it would be a bad choice to use Sodium hydroxide as hand-warmer. And you should not do so.