Apparent and standard molar volumes and heat capacities of aqueous Ni(ClO4)2 from 25 to 85°C

Abstract

Apparent molar heat capacities and volumes of aqueous Ni(C104)2 were measured from 25 to 85°C over a concentration range of 0.02 to 0.8 mol-kg-1 using a Picker flow microcalorimeter and a Picker vibrating-tube densimeter. An extended Debye-Huckel equation was fitted to the experimental data to obtain expressions for the apparent molar properties as functions of ionic strength for Ni(ClO4)2(aq). The standard-state partial molar properties for Ni(C104)2(aq) in the temperature range 25 to 85°C were obtained and can be expressed by empirical equations as 97787\(\bar C_p^o \left( {Ni(ClO_4 } \right)_2 /J - K^{ - 1} - mol^{ - 1} = 2271.1 - \frac{{97787}}{{T - 190}} - 4.9\) and\(\bar V^o \left( {Ni(ClO_4 } \right)_2 /cm^3 - mol^{ - 1} = 242.43 - \frac{{8563.7}}{{T - 190}} - 0.34927T\) withT in K. The standard partial molar heat capacities and volumes for Ni2+ (aq) from 25 to 86°C were obtained by using the additivity rule and data for ClO- 4(aq) in the literature. These values were extrapolated to 300°C by employing the Helgeson-Kirkham-Flower (HKF) equations, amended to include a standard-state correction term.