scholarly journals Calorimetric study of melts in the System KF - K2NbF7

2008 ◽  
Vol 6 (2) ◽  
pp. 297-303 ◽  
Author(s):  
Ivan Nerád ◽  
Eva Mikšíková
Keyword(s):  
Experimental Data ◽  
Heat Capacity ◽  
Thermal Effect ◽  
Molar Heat Capacity ◽  
Enthalpy Of Mixing ◽  
Molar Enthalpy ◽  
Drop Calorimetry ◽  
Calorimetric Study ◽  
Negative Deviation ◽  
Small Negative Deviation

AbstractThe relative enthalpies of melts in the system KF - K2NbF7 were measured by drop-calorimetry at the temperatures 1058, 1140 and 1208 K as a function of composition. Heat capacities of melted mixtures and enthalpies of mixing were determined using the experimental data. The molar heat capacity of melts diverges slightly from additivity. The molar enthalpy of mixing of melts shows small negative deviation from ideality which decreases with decreasing temperature. The thermal effect at mixing was assigned predominantly to association reactions producing more complex fluoroniobate anions.

scholarly journals Calorimetric study of melts in the system KF - K2TaF7

2009 ◽  
Vol 7 (4) ◽  
pp. 774-779 ◽  
Author(s):  
Ivan Nerád ◽  
Eva Mikšíková ◽  
Zuzana Balogová
Keyword(s):  
Heat Capacity ◽  
Thermal Effect ◽  
Molar Heat Capacity ◽  
Enthalpy Of Mixing ◽  
Molar Enthalpy ◽  
Drop Calorimetry ◽  
Calorimetric Study ◽  
Negative Deviation ◽  
Increasing Temperature ◽  
Complex Anions

AbstractEnthalpy increment measurements on melts in the system KF-K2TaF7 were carried out by drop calorimetry at temperatures between 298 K and 1063, 1103 and 1143 K for selected compositions. Heat capacities of the melted mixtures and enthalpies of mixing have been determined. Careful calorimetric experiments showed small but distinct non-ideality of the melt. The molar heat capacity of melt exhibits small positive divergence from additivity. The molar enthalpy of mixing shows negative deviation from ideality which decreases with increasing temperature. The thermal effect at mixing was assigned predominantly to association reactions producing more complex fluorotantalate anions. The formation of complex anions with lower coordination number of Ta may not be excluded.

scholarly journals TEMPERATURE DEPENDENCE OF HEAT CAPACITY SCANDIUM, YTTRIUM, CERIUM, PRASEODYMIUM, NEODYMIUM AND EUROPIUM

InterConf ◽  
2021 ◽  
pp. 549-553
Author(s):  
Z. Nizomov ◽  
R. Saidzoda (Saidov) ◽  
J. Sharipov ◽  
B. Gulov
Keyword(s):  
Experimental Data ◽  
Heat Capacity ◽  
Temperature Dependence ◽  
Molar Heat Capacity ◽  
Statistical Criterion

Using the Sigma Plot program, using the available experimental data on the heat capacity of scandium, yttrium, praseodymium, cerium, neodymium, lanthanum, and europium, the equations of the temperature dependence of the specific and molar heat capacity were established. The optimal degrees for the temperature in these equations were determined using the Fisher statistical criterion. It is revealed that the general form of the temperature dependence of the heat capacity for these metals is a four-term polynomial in the form C (T) = a + b T + c T2 + d T3.

Thermochemistry of uranium compounds. XVI. Calorimetric determination of the standard molar enthalpy of formation at 298.15 K, low-temperature heat capacity, and high-temperature enthalpy increments of UO2(OH2)•H2O (schoepite)

1988 ◽  
Vol 66 (4) ◽  
pp. 620-625 ◽  
Author(s):  
I.R. Tasker ◽  
P. A. G. O'Hare ◽  
Brett M. lewis ◽  
G. K. Johnson ◽  
E. H. P. Cordfunke
Keyword(s):  
Heat Capacity ◽  
High Temperature ◽  
Low Temperature ◽  
Thermodynamic Properties ◽  
Enthalpy Of Formation ◽  
Molar Heat Capacity ◽  
Temperature Drop ◽  
Molar Enthalpy ◽  
Standard Molar Enthalpy ◽  
Enthalpy Increments

Three precise calorimetric methods, viz., low-temperature adiabatic, high-temperature drop, and solution-reaction, have been used to determine as a function of temperature the key chemical thermodynamic properties of a pure sample of schoepite, UO2(OH)2•H2O. The following results have been obtained at the standard reference temperature T = 298.15 K: standard molar enthalpy of formation [Formula: see text] molar heat capacity [Formula: see text] and the standard molar entropy [Formula: see text] The molar enthalpy increments relative to 298.15 K and the molar heat capacity are given by the polynomials: [Formula: see text] and [Formula: see text], where 298.15 K < T < 400 K. The present result for [Formula: see text] at 298.15 K has been combined with three other closely-agreeing values from the literature to give a recommended weighted mean [Formula: see text] from which is calculated the standard Gibbs energy of formation [Formula: see text] at 298.15 K. Complete thermodynamic properties of schoepite are tabulated from 298.15 to 423.15 K.

Approximation of adsorption heats of carbon monoxide on transition metals by means of an empirical model

1983 ◽  
Vol 48 (10) ◽  
pp. 2735-2739
Author(s):  
Jiří Fusek ◽  
Oldřich Štrouf ◽  
Karel Kuchynka
Keyword(s):  
Carbon Monoxide ◽  
Heat Capacity ◽  
Transition Metals ◽  
Molar Heat Capacity ◽  
Metal Adsorption ◽  
Heat Of Fusion ◽  
Class Structure ◽  
Fundamental Parameters ◽  
Adsorption Heats ◽  
Pauling Electronegativity

The class structure of transition metals chemisorbing carbon monoxide was determined by expressing the following fundamental parameters in the form of functions: The molar heat capacity, the 1st and 2nd ionization energy, the heat of fusion, Pauling electronegativity, the electric conductivity, Debye temperature, the atomic volume of metal. Adsorption heats have been predicted for twelve transition metals.

Heat capacities and enthalpies of fusion and transformation for solvates of some salts with dimethyl sulfoxide and dimethylformamide

1988 ◽  
Vol 53 (12) ◽  
pp. 3072-3079
Author(s):  
Mojmír Skokánek ◽  
Ivo Sláma
Keyword(s):  
Heat Capacity ◽  
Phase Transformation ◽  
Phase Transformations ◽  
Dimethyl Sulfoxide ◽  
Liquidus Temperature ◽  
Molar Heat Capacity ◽  
Solid Phase ◽  
Zinc Nitrate ◽  
Heat Capacities ◽  
Liquid Phases

Molar heat capacities and molar enthalpies of fusion of the solvates Zn(NO3)2 . 2·24 DMSO, Zn(NO3)2 . 8·11 DMSO, Zn(NO3)2 . 6 DMSO, NaNO3 . 2·85 DMSO, and AgNO3 . DMF, where DMSO is dimethyl sulfoxide and DMF is dimethylformamide, have been determined over the temperature range 240 to 400 K. Endothermic peaks found for the zinc nitrate solvates below the liquidus temperature have been ascribed to solid phase transformations. The molar enthalpies of the solid phase transformations are close to 5 kJ mol-1 for all zinc nitrate solvates investigated. The dependence of the molar heat capacity on the temperature outside the phase transformation region can be described by a linear equation for both the solid and liquid phases.

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