CC BY
40
UDC 541.11
DOI: 10.18698/1812-3368-2020-1-93-99
NICKEL SULFATE AQUEOUS SOLUTIONS THERMAL CHEMISTRY AND ENTHALPY OF Ni2+ CATION FORMATION AT THE TEMPERATURE 298.15 K
A.A. Gurov1 [email protected]
S.V. Kozhevnikova2 A.N. Ozhogina2
S.N. Solovyev2 [email protected]
1 Bauman Moscow State Technical University, Moscow, Russian Federation
2 D. Mendeleev University of Chemical Technology of Russia, Moscow, Russian Federation
Abstract Keywords
Calorimeter with an isothermal shell was used at a tem- Dissolution enthalpy, dilution perature of 298.15 K to measure the following parame- enthalpy, thermochemical ters: enthalpy of NiSC>4(k) dissolution in water followed characteristics, ion association, by generation of two molar concentration solutions; standard compound/ion enthalpy of four NiSCU aqueous solutions dilution hav- formation enthalpies, aqueous ing various molar concentrations followed by generation solutions of solutions with approximately the same concentration values. Based on the data obtained, enthalpy and ion association constant in the NiSQi aqueous solution, as well as standard enthalpy of the aqueous solution formation, were determined for the indicated compound. The latter value made it possible to establish a more accurate value of standard enthalpy in the Ni2+ cation Received 01.07.2019 formation in an aqueous solution, which turned out to Accepted 30.09.2019 be equal to -52.3 ± 0.5 kj/mol © Author(s), 2020
Introduction. Department of General and Inorganic Chemistry of the D. Mendeleev University of Chemical Technology of Russia and the Department of Chemistry of the Bauman Moscow State Technical University are carrying out scientific and research work to redefine and specify thermo-chemical characteristics of compositions and ions formation [1]. As part of this work, the task was set to clarify the value of standard enthalpy in the Ni2+ nickel cation formation in the aqueous solution.
Nickel metal is not only the basis of such important alloys as nichrome, Monel, Hastelloy, etc., but also being an alloying constituent is a part of other materials widely used in engineering and technology [2]. Its compositions, salts in particular, which provide Ni2+ cation in solutions, are extensively employed
both in chemistry and in technology [2, 3], and are also of certain interest for biologists [3].
Standard enthalpy value of the Ni2+ cation formation provided in the most authoritative domestic [4] and foreign [5, 6] reference books possesses a relative error of about 5 %, which appears to be absolutely unsatisfactory. NiSC>4(k) nickel sulfate was selected as a reference electrolyte to find the value of this thermodynamic characteristic, since its enthalpy generation in the group of similar compositions was determined with the lowest relative error.
Experimental part. To obtain reliable results when conducting thermo-chemical measurements, two samples of crystalline nickel sulfate were used.
The first sample was synthesized from the NiCh(k) anhydrous salt, which was treated with the concentrated solution of sulfuric acid. At the end of the chemical reaction and after cessation of the HC1 evolution, the solution was evaporated to dryness. Dry residue after calcination on a sand bath was dissolved in a small amount of distilled water accompanied by heating. The resulting solution was filtered. The filtrate was evaporated at the temperature of 70-80 °C before the crystal haze. Then, the contents were cooled to room temperature. Hazed crystals of nickel sulfate appearing during this procedure were separated using the Buchner funnel. After preliminary drying between the filter paper sheets, crystals were placed in a desiccator above the open surface of P2C>5(k) for further dehydration and storage.
The second sample of nickel sulfate was obtained from its crystalline hydrate by carefully heating the latter under reduced pressure for 2 hours [7, 8]. Chemical reagents used in the synthesis of samples had purity characteristics not lower than the chemically pure class.
Residual water content in the obtained samples of anhydrous NiS04(k) determined by titration according to the Fisher method did not exceed 0.05 % (mass.) with the method accuracy of ± 0.01 % (mass.). Both anhydrous samples appeared to be light yellow crystals, greening in the air due to their absorption of water. They were stored in closed containers in a dry chamber above the P20s(k) open surface. When measuring the dissolution enthalpy in water and the enthalpy of aqueous solutions dilution, no differences in behavior were observed between them.
Thermochemical measurements were performed in a calorimeter with an isothermal shell [9], which had the following characteristics: thermometric sensitivity: 5-10"5 K: calorimetric sensitivity: 0.05 J;
thermometer (thermistor) resistance at the temperature 298.15 K: 10020 Q;
thermometer resistance temperature coefficient: 350 Q/K;
accuracy of maintaining constant temperature of the isothermal shell: ± 0.005 K.
Calorimetric liquid mixing was carried out using a magnetic mixer. Calorimeter thermal value was determined by electrical technique with a systemic error of not more than 0.1 %. Reliability of the calorimetric installation was checked by measuring the KCl(k) dissolution enthalpy in water accompanied by generation of a molar concentration solution equal to 0.02 mol/kg. The obtained value of this characteristic, i.e., 17.45 ± 0.08 kj/mol, coincided within the error with the most reliable literature data [10].
Results of measuring the NiS04(k) dissolution enthalpy in water and the enthalpy of this salt solutions dilution, i.e., the electrolyte, are presented in Tables 1 and 2.
Table 1
Values of the dissolution enthalpy AHs NiSO^k) in water at the temperature 298.15 К
Initial temperature during the experiment to, П Heat exchange correction 8,Q Corrected temperature raise during the experiment ARc> £2 Salt batch weight ms NiS04(k), mg Quantity of heat generated during the experiment due to dissolution Q. J Dissolution enthalpy AHs, kj/mol
Cmav ~ 0.0018 mol/kg; AHs.av = -89.4 ±0.1 kj/mol
10032.18 -0.52 -10.36 50.24 29.02 -89.4
10027.37 0.44 -9.48 45.81 26.55 -89.7
10020.56 0.68 -10.10 49.16 28.30 -89.1
10027.49 -0.05 -11.21 54.29 31.40 -89.5
10039.11 0.27 -11.34 55.07 31.77 -89.3
Cfflflv = 0.0030 mol/kg; AHs.av = -89.2 ±0.1 kj/mol
10045.91 0.68 16.49 80.27 46.20 -89.1
10031.82 -0.16 16.78 81.56 47.01 -89.2
10037.13 -0.08 17.49 85.21 48.99 -89.0
10029.69 -0.08 17.62 85.94 49.37 -88.9
10018.23 -0.55 16.34 79.13 45.76 -89.5
Note. Cm av is solution molal concentration average value; AHS. av is dissolution enthalpy average value.
Table 2
Values of the dilution enthalpy Aifdu of NiS04 aqueous solutions at the temperature 298.15 K
Initial temperature during the experiment t0, Q Heat exchange correction 8, Q Corrected temperature raise during the experiment ARa Q Quantity of heat generated during the experiment due to dissolution Q, J Dilution enthalpy Affdü, kj/mol
10020.18 Cmin - 0.2780 m Al 0.105 ol/kg; Cmf- 0.003S Idilav = -1.38 ±0.0 -0.342 mol/kg; Van - 2 2 kj/mol 0.959 .5 ml; -1.38
10021.37 0.127 -0.352 0.987 -1.42
10022.44 0.134 -0.332 0.931 -1.34
10020.95 0.096 -0.340 0.952 -1.37
10018.21 Cmi„ = 0.1390 m Al -0.056 ol/kg, Cmf = 0.0035 idilav— 1.32 i 0.0 -0.328 mol/kg; Vdu = 5 2 kj/mol 0.917 .0 ml; -1.32
10020.76 -0.078 -0.337 0.945 -1.36
10020.36 -0.094 -0.318 0.890 -1.28
10015.18 -0.102 -0.330 0.924 -1.33
10027.29 Cmi„= 0.0695 m< Al 0.094 ol/kg, Cmf= 0.0035 idilav^-1.03 ±0.0 -0.256 mol/kg; Van = 10 2 kj/mol 0.716 .0 ml; -1.03
10029.42 0.083 -0.261 0.730 -1.05
10015.87 -0.075 -0.251 0.702 -1.01
10011.61 -0.066 -0.253 0.709 -1.02
( 10017.00 2m¡n = 0.0348 m AH, -0.047 ol/kg Cmf= 0.0035 ui. av =-0.584 ±0.0 0.145 mol/kg; Vdu = 2C 04 kj/mol 0.407 10 ml; -0.585
10018.14 -0.064 0.148 0.414 -0.595
10030.92 0.028 0.143 0.400 -0.574
10028.81 Note. Cmin are dilution er 0.036 and C„f are mo] ithalpy average 0.145 al concentrations values; Van is dilute 0.406 af initial and fins id solution volur -0.583 il solutions; AHdii. av ne.
Experimental data processing, results and discussion. Thermochemical data on dilution enthalpies were processed within the framework of the existing concept on a present equilibrium in solution between ions and an ion pair of the
same type [11, 12] in cases of describing a solution of totally ionized electrolyte of any concentration using the Debye — Hiickel theory. Source data for such processing are given in Table 3. As a result of processing the obtained data, enthalpy and ion association constant in the N1SO4 aqueous solution were determined, which constituted the following:
Ai/ass = 5 ± 1 kj/mole; = 500 ± 10.
Table 3
NiS04 solution dilution enthalpy at the temperature 298.15 K
Molar concentration in solutions, mol/kg NiS04 solution dilution enthalpy, kj/mol Enthalpy difference: AHdn. exp — AH ¿a d - н> kj/mol
initial, с final, Ст f experimentally determined AHan. e*p calculated based on the Debye — Hiickel theory [13], AHdii. D-H
0.2780 0.0035 -1.380 ± 0.020 -3.05 ± 0.40 1.67 ± 0.40
0.1390 0.0035 -1.320 ± 0.020 -2.67 ± 0.35 1.35 ± 0.35
0.0695 0.0035 -1.030 ± 0.020 -2.07 ± 0.30 1.04 ± 0.30
0.0348 0.0035 -1.584 ± 0.004 -1.30 ± 0.20 0.72 ± 0.20
Calculations demonstrate that in the studied solutions of a molar concentration equal to 0.0018 and 0.0030 mol/kg, degree of dissociation of ion pairs is close to 1, i.e., 0.998 and 0.997, respectively.
The AHg NiS04(k) standard dissolution enthalpy in water was calculated by the ratio [14]:
AH° = AHS . av + (1 - a)AHdis + AHdii.D-H,
where AHs.av is the dissolution enthalpy (average value) accompanied by generation of the Cm av molar concentration solution; a is the degree of dissociation of ion pairs; AHdis is the enthalpy of the ion pairs dissociation, while AHdis = -Afiass; AHdii. d - h is the enthalpy of diluting the Cm molar concentration solution accompanied by generation of an infinitely diluted solution calculated on the basis of the Debye — Hiickel theory in the second approximation.
In regard to the two mentioned above solutions, this characteristic value would be as follows:
AHs° = (-89.4 ± 0.1) + (1 - 0.998) (-5) + (-0.42 ± 0.05) = -89.8 ± 0.1 kj/mol;
AHs° = (-89.2 ± 0.1) + (1 - 0.997) (-5) + (-0.50 ± 0.05) = -89.7 ± 0.1 kj/mol.
In this case, the AH° av average value is equal to -89.75 ±0.1 kj/mol. Then, the N1SO4 standard formation enthalpy in the aqueous solution is equal to:
AfH° =A +AHs°av= (-873.5 ±0.5) + (-89.75 ±0.10) =
/ N1SO4 (s. St) / N1SO4 (k) ' v '
= -963.3 ± 0.5 kj/mol.
Value of the standard crystalline nickel sulfate formation enthalpy equal to -873.5 ± 0.5 kj/mol was taken from paper [4].
It is known that the NiSCU standard formation enthalpy solution is the total of standard enthalpies of Ni2+ and SO^- ions formation. For the last particle, the value of this characteristic constitutes -911.0 ± 0.2 kj/mol, according to the reference book [15]. Hence, taking into account the above, the Ni2+ ion standard formation enthalpy in an aqueous solution is equal to:
f №(s!st) f NlS°4(s.st) f SO^sst)
= (-963.3 ± 0.5) - (-911.0 ± 0.2) = -52.3 ± 0.5 kj/mol. Conclusion. Based on thermochemical measurements, a reliable value of the Ni2+ nickel cation standard enthalpy formation in an aqueous solution was obtained equal to -52.3 ± 0.5 kj/mol, and with an error that should be noted significantly lower than the current value used in this thermochemical characteristic.
REFERENCES
[1] Gorchakova E.A., Gurov A.A., Solov'yev S.N. Standard enthalpy of ion Cu2+ formation in aqueous solution. Herald of the Bauman Moscow State Technical University, Series Natural Sciences, 2018, no. 3, pp. 104-111 (in Russ.).
DOI: https://doi.org/10.18698/1812-3368-2018-3-104-lll
[2] Gurov A.A., Slitikov P.V., Mednykh Zh.N. Metally i splavy [Metals and alloys]. Moscow, BMSTU Publ., 2018.
[3] Greenwood N.N., Earnshaw A. Chemistry of the elements. Butterworth-Heinemann, 1997.
[4] Glushko V.P., ed. Termicheskie konstanty veshchestv. Vyp. 6 [Thermal constants of materials. Iss. 6]. Moscow, VINITI Publ., 1972.
[5] Cox J.D., Wagman D.D., Medvedev V.A., eds. CODATA key values of chemical thermodynamics. Hemisphere Publ. Corp., 1989.
[6] Rossini F.D., Wagman D.D., Evans W.H., et al. Selected values of chemical thermodynamic properties. Government Printing Office, 1952.
[7] Karyakin Yu.V., Angelov I.I. Chistye khimicheskie veshchestva [Pure chemicals]. Moscow, Khimiya Publ., 1975.
[8] Zaytsev O.S. Issledovatel'skiy praktikum ob obshchey khimii [Research workshop on general chemistry], Moscow, Izd-vo MGU Publ., 1994.
[9] Solovev S.N., Shatalov K.I., Dupal A.Ya. Standard enthalpy of formation of crystalline Ca[NiFs]. Russ. J. Phys. Chem., 2014, vol. 88, iss. 5, pp. 893-895.
DOI: https://doi.Org/10.l 134/S003602441405032X
[10] Glushko V.P., ed. Termicheskie konstanty veshchestv. Vyp. 10. Ch. 2 [Thermal constants of materials. Iss. 10. P. 2]. Moscow, VINITI Publ., 1981.
[11] Solovyev S.N., Khekalo T.V. Determination of electrolytes association thermody-namical properties in solution using hermochemistry measurements. Trudy RKhTU im. D.I. Mendeleeva, 1989, no. 158, pp. 129-138 (in Russ.).
[12] Marcus Y., Hefter G. Ion pairing. Chem. Rev., 2006, vol. 106, iss. 11, pp. 4583-4611. DOI: https://doi.org/10.1021/cr040087x
[13] Solovyev S.N., Privalova N.M., Vorobyev A.F. About application of Debye — Hiickel theory for enthalpy calculation of non-aqueous solution dilution electrolytes. Zhurnal fizicheskoy khimii, 1976, vol. 50, no. 10, pp. 2719-2720 (in Russ.).
[14] Mishchenko K.P., Poltoratskiy G.M. Termodinamika i stroenie vodnykh i nevodnykh rastvorov elektrolitov [Thermodynamics and structure of aqueuos and non-aqueuos electrolytes solutions]. Leningrad, Khimiya Publ., 1976.
[15] Glushko V.P., ed. Termicheskie konstanty veshchestv. Vyp. 2 [Thermal constants of materials. Iss. 2]. Moscow, VINITI Publ., 1966.
Gurov A.A. — Cand. Sc. (Chem.), Assoc. Professor, Department of Chemistry, Bauman Moscow State Technical University (2-ya Baumanskaya ul. 5, str. 1, Moscow, 105005 Russian Federation).
Kozhevnikova S.V. — Cand. Sc. (Chem.), Assoc. Professor, Department of General and Inorganic Chemistry, D. Mendeleev University of Chemical Technology of Russia (Miusskaya ploshchad 9, Moscow, 125047 Russian Federation).
Ozhogina A.N. — Bachelor's Degree Student, Department of General and Inorganic Chemistry, D. Mendeleev University of Chemical Technology of Russia (Miusskaya ploshchad 9, Moscow, 125047 Russian Federation).
Solovyev S.N. — Dr. Sc. (Chem.), Professor, Head of the Department of General and Inorganic Chemistry, D. Mendeleev University of Chemical Technology of Russia (Miusskaya ploshchad 9, Moscow, 125047 Russian Federation).
Please cite this article as:
Gurov A.A., Kozhevnikova S.V., Ozhogina A.N., et al. Nickel sulfate aqueous solutions thermal chemistry and enthalpy of Ni2+ cation formation at the temperature 298.15 K. Herald of the Bauman Moscow State Technical University, Series Natural Sciences, 2020, no. 1 (88), pp. 93-99. DOI: http://doi.org/10.18698/1812-3368-2020-l-93-99
