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在298.15K下利用具有恒温环境的溶解-反应热量计,测定了VOSO4·2.76H2O(s)在水和0.5mol·kg-1硫酸水溶液中的摩尔溶解焓.在硫酸水溶液中VOSO4·2.76H2O(s)摩尔溶解焓的负值比在纯水中要小很多,这说明VOSO4在硫酸水溶液中具有较高的能量状态.借助VOSO4水溶液的离子缔合平衡和硫酸的二级解离平衡,改进了Archer方法,并用这种改进的方法分别估算了VOSO4·2.76H2O(s)在水中的标准摩尔溶解焓△sHm=-29.18kJ·mol-1,以及在0.5mol·kg-1硫酸水溶液中的标准摩尔溶解焓△sHm=-25.79kJ·mol-1.根据离子缔合平衡和硫酸二级解离平衡的计算结果,硫酸根离子浓度受到硫酸二级解离平衡控制,使部分[VOSO4]0离子对解离,致使硫酸氧钒-硫酸水溶液中的自由氧钒离子(VO2+)增加.
The molar enthalpy of solution of VOSO4 · 2.76H2O (s) in water and 0.5 mol · kg-1 sulfuric acid aqueous solution was measured at 298.15 K using a solution-reaction calorimeter with constant temperature. The molar ratio of VOSO4 · 2.76H2O s), the negative value of molar enthalpy of dissolution is much smaller than that of pure water, which indicates that VOSO4 has a higher energy state in aqueous sulfuric acid solution.With the balance of ionic association of VOSO4 aqueous solution and the secondary dissociation equilibrium of sulfuric acid, Archer method, and the improved method was used to estimate the standard molar enthalpy of adsorption of VOSO4 · 2.76H2O (s) △ sHm = -29.18 kJ · mol-1 in water and the standard of 0.5 mol · kg-1 sulfuric acid aqueous solution Molar enthalpy of solution △ sHm = -25.79kJ · mol-1. According to the results of ion association equilibrium and secondary dissociation of sulfuric acid, the concentration of sulfate ions is controlled by the secondary dissociation of sulfuric acid and some [VOSO4] 0 ions On the dissociation, resulting in vanadyl sulfate - sulfuric acid solution of free oxygen vanadium (VO2 +) increased.