复盐K_2Ni(IO_3)_4·2H_2O的热化学研究

Thermochemical investigations of a double salt K 2Ni(IO 3) 4·2H 2O

用溶解量热法，以水为量热溶剂，根据 Ｈｅｓｓ 定律设计了一个热化学循环，用新型的具有恒定温度环境的反应热量计分别测定了以下两个过程的溶解热：２ Ｋ Ｉ Ｏ３＋ Ｎｉ（ Ｉ Ｏ３）２＋ Ｈ２ Ｏ Ｋ＋（ａｑ）＋ Ｎｉ２＋（ａｑ）＋ Ｉ Ｏ３－ （ａｑ）， Ｋ２ Ｎｉ（ Ｉ Ｏ３）２·２ Ｈ２ Ｏ＋ Ｈ２ Ｏ Ｋ＋（ａｑ）＋ Ｎｉ２＋（ａｑ）＋ Ｉ Ｏ３－ （ａｑ）． 并根据 相关数据 求得 Ｋ２ Ｎｉ（ Ｉ Ｏ３ ）４ ·２ Ｈ２ Ｏ 在 ２９８． ２ Ｋ 时 的标 准生 成焓， 其值 为－ ２ １２７．２０ ｋ Ｊ·ｍ ｏｌ－ １ ，同时根据该化合物的 Ｄ Ｓ Ｃ 数据估算了 Ｋ２ Ｎｉ（ Ｉ Ｏ３）４ ·２ Ｈ２ Ｏ 的生成焓。

The molar dissolution enthalpies of the two processes: 2KIO 3+Ni(IO 3) 2 + H 2O K + (aq) + Ni 2+ (aq) + IO 3 - (aq) , K 2Ni(IO 3) 4·2H 2O + H 2O K + (aq) + Ni 2+ (aq) + IO 3 - (aq) . have been determined by solution calorimtry in a isoperibel reaction calorimeter.The calorimetric solvent is water. According to the Hess Law,we design a rational thermochemical cycle.From the results and other auxiliary quantities, the standard enthalpy of formation( △ fH θ m,298.2 K = -2 127.20 kJ·mol -1 )of a double salt K 2Ni(IO 3) 4·2H 2O is obtained. Simultaneously,the △ fH θ 298 K K 2Ni(IO 3) 4·2H 2O is calculated from the recorded △H 0 of the DSC curve.The values of △ fH θ 298 K K 2Ni(IO 3) 4·2H 2O determined by the two methods, are compared.