氢氧化钠分解氟化钙的热力学分析

Thermodynamic Analysis for Decomposition of Calcium Fluoride by Sodium Hydroxide

根据热力学计算结果,绘制出25℃下NaOH分解氟化钙的Ca-F-H_2O体系溶解组分的lgc-pH图。根据计算结果和所绘制的热力学平衡图对氢氧化钠分解氟化钙进行分析,结果表明:当pH<4时,F^-迅速减少,Ca^(2+)迅速增加,氟化钙不能稳定存在;当4≤pH≤12时,氟化钙能够稳定存在;当pH>12时,Ca^(2+)迅速减少,F^-迅速增加,氟化钙开始分解产生Ca(OH)_(2(aq));当pH继续升高到14.4时,Ca(OH_(2(aq))达到饱和,开始形成Ca(OH)_(2(s))沉淀。

Diagrams of lgc-pH for dissolving components in the system of Ca-F-H2 O where sodium hydroxide decomposed calcium fluoride at 25 ℃ were drawed based on thermodynamic calculation data.According to the calculation results and the thermodynamic equilibrium diagram,the behavior of sodium hydroxide decomposing calcium fluoride was analyzed.The results show that at pH4,Fdecreased rapidly,Ca^2＋increased rapidly,and calcium fluoride is not stable,and at 4≤pH≤12,calcium fluoride can exist stably,and at pH12,Ca^2＋ reduced quickly,F^-increased rapidly,calcium fluoride started to decompose to generate Ca（OH）2（aq）.When the pH rises up to 14.4,Ca（OH）2（aq）saturates and Ca（OH）2（s）precipitates.