氯化镁及其水合物的标准溶解焓与生成焓

Standard Enthalpies of Solution and Formation for Magnesium Chloride and its Hydrates

利用精密量热仪测定了MgCl_2、MgCl_2·2H_2O、MgCl_2·4H_2O和MgCl_2·6H_2O在298.15°K溶于水的积分溶解热,并利用Pitzer电解质溶液的。~ΦL方程,计算了溶质的相对表观摩尔热焓,从而得到标准溶解焓分别为(KJ·mol^(-1))—155.86±0.17、—79.45±O.17,—41.78±O.18和—14.58±0.16;晶格能分别为—2490.36,—3158.37,—3772.70和—4376.56。二、四、六水合物的标准生成焓分别为—1289.39,—1898.72和—2497.58;水合焓分别为—76.41,—114.08和—141.28。

The integral heats of solutioil for MgCl_2·2H_2O, MgCl_2·4H_2O and MgCl_2·6H_2O in pure water have been determined at 25℃, by precision calorimeter. The relative apparent mol enthalpies of MgCl_2 and its hydrates have been calculated with the aid of Pitzers theory of eleetrolyte Solution. Thus the standard enthalpies of Solution△H_8~0(MgCl_2)=155.86±0.17; (MgCl_2·2H_2O)=-79.45±0.17; (MgCl_2·4H_2O)=-41.78±0.18; (MgCl_2·6H_2O)=-14.58±0.16 KJ·mol^(-1) and the standard enthalpies of formation△H_f^0(MgCl_2·2H_2O)=-1289.39; (MgCl_2·4H_2O)=-1898.72; (MgCl_2·6H_2O)=-2497.58 KJ·mol^(-1)have been obtained repectively.