Standard enthalpy of formation of nickel trifluoride by isothermal calorimetry

Article abstract of DOI:10.1134/S0036024412030296

The change in enthalpy in reactions of NiF₃(s) with water and aqueous solution of potassium hydroxide are measured in the isothermal calorimetry mode at 298.15 K. The standard enthalpy of formation Δ_fH° of nickel trifluoride was foun

Full text of DOI:10.1134/S0036024412030296

ISSN 0036ꢀ0244, Russian Journal of Physical Chemistry A, 2012, Vol. 86, No. 3, pp. 516–518. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © S.N. Solov’ev, A.A. Korunov, K.G. Zubkov, A.A. Firer, 2012, published in Zhurnal Fizicheskoi Khimii, 2012, Vol. 86, No. 3, pp. 590–592.
BRIEF
COMMUNICATIONS
Standard Enthalpy of Formation of Nickel Trifluoride
by Isothermal Calorimetry
S. N. Solov’ev, A. A. Korunov, K. G. Zubkov, and A. A. Firer
Mendeleev University of Chemical Technology, Moscow, 125047 Russia
eꢀmail: snsol@muctr.ru
Received November 9, 2010
Abstract—The change in enthalpy in reactions of NiF3(s) with water and aqueous solution of potassium
hydroxide are measured in the isothermal calorimetry mode at 298.15 K. The standard enthalpy of formation
Δ
fH° of nickel trifluoride was found to be –816
6 kJ/mol.
Keywords: isothermal calorimetry, enthalpy of formation, water, nickel trifluoride.
DOI: 10.1134/S0036024412030296
INTRODUCTION
was beyond the measurement error, and the calorimeꢀ
ter’s heat capacity (0.1601 0.0003 J/ ) was thereꢀ
Ω
As part of our research program, we are interested
in the thermodynamic and structural (NiF3 or
Ni[NiF6]) properties of hexafluoronickelates(IV) [1–
4] which are promising oxidative reagents. Here we
present our work on determining the enthalpy formaꢀ
tion of NiF3(s) from calorimetric experiments.
fore used for all heat calculations. This was deterꢀ
mined by monitoring changes in the resistance of the
thermistor after filling the calorimetric cell with 120 g
of water and passing known amounts of electric curꢀ
rent thought the heater. The systematic error in meaꢀ
suring the heat capacity of the calorimeter did not
exceed 0.1%
.
EXPERIMENTAL
The reaction of NiF3 with water yielded a pale
green solution, while the interaction with aqueous
potassium hydroxide resulted in a suspension from
which a greenish precipitate easily soluble in mineral
acids was formed when left standing.
The studied samples of nickel trifluoride were synꢀ
thesized by V.B. Sokolov and A.V. Ryzhkov at the Kurꢀ
chatov Institute National Research Centre. The specꢀ
imens were found to be homogeneous (single phase)
and stoichiometric (accuracy, 1%) from the results of
Xꢀray diffraction phase and quantitative chemical
analyses, respectively.
The thermochemical measurements were perꢀ
formed using an isothermal calorimeter [5] with a therꢀ
mometric and calorimetric sensitivity of 1.2
Extra precautions were taken while working with
KOH solutions to avoid contamination with carbonꢀ
ates.
A number of chemical analyses were performed to
determine the composition of the reaction mixtures
after conducting the calorimetric experiments. The
concentration of fluoride ions was thus established by
titration with thorium nitrate and sodium alizarin sulꢀ
fonate as an indicator (accuracy, 1%). Titration with
standardized solutions of HCl or KOH was used to
find the total basicity or acidity, respectively, of reacꢀ
tion solutions (accuracy, 0.5%). Titration with a
standardized Trilon B solution was performed (accuꢀ
racy, 1%) to determine the concentration of
nickel(II) ions in the investigated solutions (obtained
directly from calorimetric experiments or prepared by
dissolving Ni(OH)2 precipitate in an acid).
×
10–5
K
and 0.01 K, respectively. The accuracy of maintaining
temperature via a thermostat was 0.005 K. A semiꢀ
conductor resistance thermometer of 77350
used at 298.15 K to monitor changes in temperature
(3500 per 1 K).
It was established in a series of experiments that the
interaction of 1 mol of nickel trifluoride with water or
aqueous potassium alkali yields 0.5 mol of gaseous
oxygen (accuracy, 1%).
Ω
was
Ω
RESULTS AND DISCUSSION
The results from our calorimetric experiments are
Our analyses allowed us to conclude that water is
given in the table below. It should be noted that the difꢀ oxidized into molecular oxygen upon the reaction of
ference between the heat capacity of the investigated nickel trifluoride with aqueous solutions. The other
centimolal solutions and the heat capacity of water products were HF and NiF2 when reacting with pure
516

STANDARD ENTHALPY OF FORMATION OF NICKEL TRIFLUORIDE
517
Results from calorimetric experiments (298.15 K) on the reaction between NiF3(s) and water and NiF3(s) and 0.05 molal
solution of KOH
R0,
Ω
δ
,
Ω
–
Δ
R,
Ω
q, mg
Q, J
–
Δ
H, kJ/mol
Water
77570.17
77593.54
77599.23
77589.76
77505.37
77496.88
77568.45
77510.59
77486.46
77601.81
16.26
18.41
195.75
208.43
212.55
201.06
209.93
251.28
190.13
197.50
245.91
203.00
40.28
45.41
42.79
39.83
41.15
50.04
40.95
43.29
47.94
41.09
31.34
33.37
34.03
32.19
33.61
40.23
30.44
31.62
39.37
32.50
90.0
85.0
92.0
93.5
94.5
93.0
86.0
84.5
95.0
91.5
23.76
20.84
–14.93
–21.87
15.25
–19.66
–25.52
20.68
KOH solution
77612.38
77644.87
77568.19
77531.27
77637.83
77625.76
77522.34
77631.95
77519.71
77642.11
32.15
36.42
334.23
349.03
286.51
371.96
392.50
306.37
323.17
327.98
365.90
345.47
35.78
38.94
32.16
40.29
42.76
34.81
35.63
38.77
40.95
37.86
53.51
55.88
45.87
59.55
62.84
49.05
51.74
52.51
58.58
55.31
173
166
165
171
170
163
168
171
166
169
–15.56
–29.51
40.74
32.62
–35.39
38.68
–39.47
40.78
Note: R is the initial resistance of the thermistor, δ is the correction factor for heat transfer, ΔR is the corrected value of temperature change,
0
q is the sample weight, Q is the amount of reaction heat produced, ΔH is enthalpy of the reaction, σ is the standard deviation, and
t
is the Student tꢀdistribution parameter; for water: ΔH = –91 kJ/mol, σ = 1 kJ/mol, σt
= 3 kJ/mol; for solution of KOH;
0.05
av
0.05
ΔH = –168 kJ/mol, σ = 1 kJ/mol, σt
= 2 kJ/mol.
av
0.05
water, and KF, Ni(OH)2 precipitate, and excessive HF–H2O and KOH–KF–H2O systems that would
KOH if a potassium alkali solution was used.
The thermochemical equations of studied reacꢀ
tions are therefore
exceed 0.4 kJ per mol of NiF2 or KF in a range of
concentration range similar to ours. According to
[1], the oxygen that evolved during the reaction
stayed dissolved in the water when the amount of
hexafluoronickelates(IV) reacting with aqueous
NiF3(s) + 17921H2O(l) = NiF2(soln1)
+ (1/4)O2(soln1) + HF(soln1)
+ 17920 ⋅ 5H2O(soln1);
solutions was less than 3.4
10–4 mol. In light of this
×
(1)
and the low concentration of working solutions, it is
reasonable to assume that the enthalpies of formation
of NiF2, HF, KF, KOH, and H2O under the condiꢀ
tions of the given calorimetric experiments are the
same as the heat of formation of these compounds in
pure water [6]. The uncertainties of all the intermeꢀ
diate variables were considered in calculating the
corresponding errors. The standard enthalpies of forꢀ
mation of NiF3(s) at 298.15 K were therefore found
Δ
H
= –90.5 2.8 kJ,
NiF3(s) + 18KOH(soln, KOH · 1111H2O)
= Ni(OH)2(s, freshly precipitated
+ 3KF(soln2) + 1/4O2(soln2)
)
(2)
+ (1/2)H2O(soln2) + 15KOH(soln2);
= –168 kJ
where soln1 is the NiF2 · HF 17920.5H2O and soln2
is the 3KF ·15KOH · 19998.5H2O
The direct calorimetric measurements in [1, 2]
showed that there are no interactions in the NiF2– –816 6 kJ/mol.
Δ
H
2
,
·
to be
⎯
817
7
and –814
9 kJ/mol for reactions (1)
.
and (2), respectively, yielding an average value of
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 86
No. 3 2012

518
SOLOV’EV et al.
2. K. I. Shatalov and S. N. Solov’ev, Russ. J. Phys. Chem.
85, 331 (2011).
CONCLUSIONS
A
A comparison of our thermochemical data with the
3. S. N. Solov’ev, K. I. Shatalov, and A. Ya. Dupal, Russ.
enthalpies of formation of other hexafluoronickeꢀ
lates(IV) [1–4] along with our analysis of the literature
data on the heat of formation of diꢀ and trifluorides of
ꢀelements [6] allow us to conclude that nickel trifluꢀ
oride compound exists in the Ni[NiF6] molecular
J. Phys. Chem. A 85, 1855 (2011).
4. K. I. Shatalov and S. N. Solov’ev, in Proceedings of the
17th International Conference on Chemical Thermodyꢀ
namics in Russia, 2009 (Kazan. Gos. Univ., Kazan,
2009), Vol. 2, p. 150.
d
form.
5. T. V. Lazukina and S. N. Solov’ev, Dep. VINITI 28.06–
06 No. 870ꢀB (2006).
REFERENCES
6. Thermal Constants of Substances, The Handbook,
Ed. by V. P. Glushko (VINITI, Moscow, 1965–1981),
Nos. 1–10 [in Russian].
1. S. N. Solov’ev and K. I. Shatalov, Russ. J. Phys. Chem.
A
83, 1053 (2009).
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Vol. 86
No. 3 2012