Studies On The Mean Activity Coefficient Of Na⁺,K⁺,Sr²⁺//Br^--H₂O Containing Sr Subsystems At 288.15 K And 318.15 K

In order to study the thermodynamic properties of systems containing Br and Sr in electrolyte solution,the mean activity coefficients of Na Br-Sr Br₂-H₂O（288.15 K,318.15 K）,KBr-Sr Br₂-H₂O（288.15 K,318.15 K）two ternary systems were studied by using electromotive force method.For the ternary system of Na Br-Sr Br₂-H₂O,the sodium ion selective electrode（Na-ISE）and bromide ion selective electrode（Br-ISE）are firstly used to measure electromotive forces of the system Na Br-H₂O at he corresponding temperature,then according to the Pitzer equation and Nernst equation regression,the standard cell potential E⁰ and the electrode response slope k are fitted.The experimental results show that the electrodes used in this work have a good Nernst response,it can be used to determine the electromotive force of mixed solutions.A sodium ion selective electrode（Na-ISE）and a bromide ion selective electrode（Br-ISE）electrode were used to form a liquid-free potential reversible battery:Na-ISE|Na Br（8）₁),Sr Br₂（8）₂)|Br-ISE.The mean ionic activity coefficients of Na Br in the ternary system Na Br-Sr Br₂-H₂O were researched by cell potential method.In this system,the total ionic strength I ranges from 0.01 up to 2.00 mol·kg^-1 for different ionic strength fractions y₍（7） of Sr Br₂,i.e.,₍（7）=（0.0,0.2,0.4,0.6,0.8）.The results show that the Na-ISE and Br-ISE have a great Nernst effect.The mean ionic activity coefficients of Na Br in Na Br-Sr Br₂-H₂O were calculated by Nernst equation and measured cell potential values.The Pitzer ion interaction parameters_{（6）+?2+and（6）+?2+?-were fitted by Pitzer model with experimental results in this work,and the mean ionic activity coefficients of Sr Br2 were also calculated according to the theory of the Pitzer model.At last,the osmotic coefficient,Φ,water activity,aw,excess Gibbs energy,G^E of the ternary system were also calculated.The results show that the mean activity coefficient of Sr Br2 and Na Br in the system will decrease,and the water activity,aw of the system and the excess Gibbs energy,G^E will also decrease with the increase of the total ionic strength,I.The permeability coefficient,Φof the system are always show the tendency of decrease before they are bigger with the increase of ionic strength,I.For the ternary system of KBr-Sr Br2-H2O,the potassium ion selective electrode（K-ISE）and bromide ion selective electrode（Br-ISE）firstly are used to measure the electromotive force of KBr-H2O at the corresponding temperature,then according to the Pitzer equation and Nernst equation regression,the standard cell potential E⁰ and the electrode response slope k are fitted respectively,the experimental results show that the electrode used to have a good Nernst response,it can be used to determine the electromotive force of mixed solutions.A potassium ions selective electrode（K-ISE）and a bromide ion selective electrode（Br-ISE）electrode were used to form a liquid-free potential reversible battery:K-ISE|KBr（8）1,Sr Br2（8）2}|Br-ISE.The mean ionic activity coefficients of Na Br in the ternary system KBr-Sr Br₂-H₂O were researched by cell potential method.In this system,the total ionic strength I ranges from 0.01 up to 2.00 mol·kg^-1for different ionic strength fractions y₍（7） of Sr Br₂,i.e.,₍（7）=（0.0,0.2,0.4,0.6,0.8）.The results show that the K-ISE and Br-ISE have a great Nernst effect.The mean ionic activity coefficients of KBr in KBr-Sr Br₂-H₂O were calculated by Nernst equation and measured cell potential values.The Pitzer ion interaction parameters+_?2+and+_?2+_?-were fitted by Pitzer model with experimental results in this work,and the mean ionic activity coefficients of Sr Br₂ were also calculated according to the theory of the Pitzer model.At last,the osmotic coefficient,Φ,water activity,a_w,excess Gibbs energy,G^E of the ternary system were also calculated.The results show that the mean activity coefficient of Sr Br₂ and KBr in the system will decrease,and the water activity,a_w of the system and the excess Gibbs energy,G^E will also decrease with the increase of the total ionic strength,I.The permeability coefficient,Φof the system are first decrease and then increase with the increase of ionic strength,I.According to the experimental results,the relationship between the ionic strength components and the mean activity coefficient of the four ternary systems were drawn respectively.The linear relationship between water activity,a_w,excess gibbs free energy,G^E and total ion strength,I of each ternary system were also plotted.The experimental results showed that when the ionic strength fraction y₍（7） is constant,the mean ionic activity coefficients of Na Br and Sr Br₂ in the mixed salt solution decreases with the increase of the total ionic strength,I.The water activity,a_w and excess Gibbs free energy,G^E of the system decreased with the increase of total ion strength,I.The permeability coefficient,Φof four system are first decrease and then increase with the increase of ionic strength,I.