一切化学反应都遵循守恒定律,如,质量守恒、元素守恒、电子守恒、电荷守恒等。运用守恒定律,只考虑反应的始态和终态,从而达到速解、巧解化学试题的目的。一、巧用元素守恒求解【例1】向一定量Fe、Fe2O3混合物中加入250 mL 2 mol·L-1HNO3 All chemical reactions follow the conservation laws, such as conservation of mass, conservation of elements, conservation of electrons, conservation of charge, and the like. The use of conservation law, only consider the beginning and end of the reaction, so as to achieve quick solution, clever solution to the purpose of chemistry questions. First, clever use of element conservation solution [Example 1] to a certain amount of Fe, Fe2O3 mixture by adding 250 mL 2 mol·L-1HNO3