Determination of standard molar enthalpies of formation of Bi2Mo3O12 (s), Bi2MoO6 (s), Bi6Mo2O15 (s) and Bi6MoO12 (s) by solution calorimetry

Article abstract of DOI:10.1016/j.tca.2019.178401

The standard molar enthalpies of formation of Bi₂Mo₃O₁₂ (s), orthorhombic phase of Bi₂MoO₆ (s), monoclinic phase of Bi₂MoO₆ (s), Bi₆Mo₂O₁₅ (s) an

Full text of DOI:10.1016/j.tca.2019.178401

Thermochimica Acta xxx (xxxx) xxxx
Contents lists available at ScienceDirect
Thermochimica Acta
journal homepage: www.elsevier.com/locate/tca
Determination of standard molar enthalpies of formation of Bi Mo O (s),
2
3 12
Bi MoO (s), Bi Mo O (s) and Bi MoO (s) by solution calorimetry
2
6
6
2
15
6
12
a
b
a,b
c,⁎
P.M. Aiswarya , S. Shyam Kumar , Rajesh Ganesan , T. Gnanasekaran
a
b
c
Homi Bhabha National Institute, Indira Gandhi Centre for Atomic Research, HBNI, Kalpakkam, 603 102, India
Materials Chemistry & Metal Fuel Cycle Group, Indira Gandhi Centre for Atomic Research, HBNI, Kalpakkam, 603 102, India
Former Raja Ramanna Fellow, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603 102, India
A R T I C L E I N F O
A B S T R A C T
Keywords:
The standard molar enthalpies of formation of Bi
2
Mo
3
O
12 (s), orthorhombic phase of Bi
2
MoO (s), monoclinic
6
Enthalpy of formation
Solution calorimetry
Bismuth molybdates
phase of Bi MoO (s), Bi Mo O (s) and Bi MoO (s) were determined by solution calorimetry and the values
2
6
6
2
15
6
12
obtained are (−2915.8 ± 8.2), (−1407.2 ± 7.1), (−1385.7 ± 7.3), (−3346.5 ± 21.7) and
−1
(
−2605.2 ± 20.3) kJ mol , respectively. The given uncertainties were calculated as 2σ of the mean with 0.95
level of confidence.
1
. Introduction
Liquid lead and Lead-Bismuth Eutectic alloys (LBE) are being stu-
standard molar enthalpies of formation of Bi
2
Mo
Mo
3
O
12 (s), orthorhombic
MoO12 (s)
and monoclinic phases of Bi
2
MoO
6
(s), Bi
6
2
O
15 (s) and Bi
6
at 298 K have been determined using solution calorimetry.
died as candidate coolants as well as spallation targets of accelerator
driven systems. As they are less reactive towards air and moisture, these
liquid metals are also being considered as alternate to liquid sodium
coolant in fast breeder reactors [1]. However, one of the challenges for
this use of liquid lead and LBE is the high solubility of structural steel
components in them which can ultimately cause heavy corrosion ef-
fects. Among the different alloying components of steel, nickel has≥
very high solubility in LBE and hence nickel free ferritic steels are
proposed as structural materials for LBE. Effect of solubility of other
alloying components would still be significant in a polythermal loop
when corrosion under high flow velocities over prolonged periods is
considered. Studies have shown that by the proper control of oxygen
concentration in the coolant, a protective oxide layer can be formed
over the steel surface. This oxide layer can effectively act as a barrier
between the steel surface and the coolant and can substantially reduce
the corrosion rate [2]. A detailed knowledge on the composition and
thermochemical data of this oxide layer is required to understand the
formation and stability of this passive oxide layer. In this context, the
ternary Bi-Mo-O system was investigated recently by the present au-
thors based on long term equilibration experiments [3,4]. Ten stable
2. Experimental
2.1. Materials
Bi
Alfa Aesar, USA) and MoO
ternary compounds. The Bi
about 6 h to remove any carbonate and moisture impurities present in
2
O
3
powder (≥0.9999 mass fraction purity on metal basis, M/s
powder were used for the preparation of
powder was calcined at 1023 K in air for
3
2 3
O
it. MoO required for this work was prepared by decomposing ammo-
3
nium heptamolybdate tetrahydrate (≥0.9996 mass fraction purity on
metal basis, M/s Sigma-Aldrich, USA) at 723 K in air for 24 h. The ca-
−
1
lorimetric solvent used was a mixture of 3 mol kg
NaOH and trie-
thanolamine (TEA) (≥0.99 mass fraction purity, M/s Emplura Merck,
India). The NaOH solution was prepared by dissolving appropriate
amount of NaOH in distilled water. The materials used in the experi-
ments is summarised in the Table 1.
2.2. Compound preparation
compounds, namely, Bi
2
Mo
3
O
12
,
Bi
2
Mo
2
O
9
,
Bi
2
MoO
6
,
Bi
8
Mo
3
O
21
,
The ternary compounds, namely, Bi
monoclinic phase of Bi MoO (s), Bi Mo
prepared by compacting the mixtures of Bi
appropriate molar ratios and heating them in air at 873 K for 48 h. The
2
2
Mo
15 (s) and Bi
(s) and MoO
3
O
12 (s), high temperature
MoO12 (s) were
(s) taken in
Bi14Mo
5
O
36
,
Bi
6
Mo
2
O
15
,
Bi10Mo
3
O
24
,
Bi38Mo
7
O
78
,
Bi
6
MoO12 and
2
6
6
O
6
Bi14MoO24 exist in this system. No thermochemical data of these
compounds are available in the literature. In the present work, the
2
O
3
3
⁎
Corresponding author.
E-mail address: gnani@igcar.gov.in (T. Gnanasekaran).
https://doi.org/10.1016/j.tca.2019.178401
Received 23 February 2018; Received in revised form 30 August 2019; Accepted 2 September 2019
0040-6031/ © 2019 Elsevier B.V. All rights reserved.
Please cite this article as: P.M. Aiswarya, et al., Thermochimica Acta, https://doi.org/10.1016/j.tca.2019.178401

P.M. Aiswarya, et al.
Thermochimica Acta xxx (xxxx) xxxx
Table 1
List of chemicals used, their source and purity.
No.
Chemicals
Source
Mass fraction purity
Analysis method
1
2
3
4
5
Ammonium heptamolybdate tetrahydrate
M/s. Sigma-Aldrich, USA
≥0.9996 on metal basis
≥0.9992
Manufacturer Assay
a
b
MoO
3
Prepared in this work as mentioned in Section 2.1
M/s. Alfa Aesar, USA
XRD , ICP-AES
Bi
Bi
Bi
2
2
2
O
3
Mo
≥0.9999 on metal basis
≥0.999
Manufacturer Assay
a b
c
c
3
O
12
Prepared in this work as mentioned in Section 2.2
Prepared in this work as mentioned in Section 2.2
XRD , ICP-AES , SEM/EDS
XRD , ICP-AES , SEM/EDS
a
b
MoO
6
≥0.999
orthorhombic
a
b
c
5
6
6
Bi
2
MoO
6
Prepared in this work as mentioned in Section 2.2
Prepared in this work as mentioned in Section 2.2
Prepared in this work as mentioned in Section 2.2
≥0.999
≥0.999
≥0.999
XRD , ICP-AES , SEM/EDS
monoclinic
a
b
Bi
6
6
Mo
2
O
15
XRD , ICP-AES
c
SEM/EDS
a
b
Bi
MoO12
XRD , ICP-AES
c
SEM/EDS
7
8
9
NaOH
M/s. E. Merck, India
M/s. E. Merck, India
M/s.Merck, UK
≥0.99
≥0.99
≥0.998
Manufacturer Assay
Manufacturer Assay
Manufacturer
Assay
Triethanolamine (TEA)
TRIS
1
0
HCl
M/s. E. Merck, India
In the range 0.365 to 0.380 in water
Manufacturer
Assay
a
b
c
X-ray powder diffraction.
Inductively coupled plasma atomic emission spectroscopy.
Scanning electron microscopy/energy dispersive X-ray spectroscopy.
low temperature orthorhombic phase of Bi
2
MoO
6
(s) was prepared by
conditions for the formation of complexes of TEA with bismuth and
reported that TEA forms 1:1 complex with bismuth ions. Hancock et al.
[9] found the complex was water soluble and based on differential
pulse polarography experiments, they determined the formation con-
stant (log K) of this 1:1 complex to be 9.2. The complexation of mo-
lybdenum ions with TEA was studied by Szalontai et al. [10]. Under
alkaline pH, the mononuclear molybdate anion exists in the tetrahedral
form while upon chelation with triethanolamine, it forms soluble ox-
omolybdate (VI) complexes which exist in the octahedral or distorted
octahedral configuration. It is also reported that water soluble com-
plexes of Mo-TEA could form when the ratio of Mo to TEA is 1:3 [10].
Based on the reports in literature, it is clear that both bismuth and
molybdenum oxides can form water soluble complexes with trietha-
nolamine under alkaline conditions. In the present experiments, the
ratio of metals to TEA was maintained as ∼1:80, so as to maintain a
large excess of TEA. The final solution obtained after the dissolution of
bismuth molybdates as well as the component oxides were clear and
there were no perceptible precipitates. The solubility of ternary bismuth
heating the oxide mixture at 773 K for 48 h. The reactions were per-
formed in alumina crucibles, with one intermediate grinding at the end
of 24 h of heating. The resulting products were characterized using X-
ray diffractometer (M/s Inel, France) with Cu K
α
radiation and graphite
12 (s), orthorhombic
15 (s) were matched
monochromator. The XRD patterns of Bi
2
Mo
3
O
Bi MoO (s), monoclinic Bi MoO (s) and Bi
2
6
2
6
6
Mo
2
O
with JCPDS patterns 00-021-0103, 00-084-0787, 04-009-3413 and 04-
0
18-9896, respectively [5] (Figs. 2–5). The XRD pattern of the com-
pound Bi MoO12 (s) matched with that reported by Bleijenberg et al.
6
[
6] (Fig.6). The XRD patterns of the prepared compounds showed a
good match with the JCPDS patterns and there were no additional
peaks, suggesting the phase purity of the compounds. The trace im-
purities in the prepared samples were identified by ICP-AES. The total
−3
mass fraction of the impurities was determined to be less than 1 × 10
(
Table 1). Further, the Bi/Mo ratio was determined by SEM/EDS ana-
lysis and found to be 0.67 ± 0.01, 2.00 ± 0.02, 3.00 ± 0.04 and
.00 ± 0.08 for Bi Mo 12 (s), Bi MoO (s), Bi Mo 15 (s), and
6
2
3
O
2
6
6
2
O
Bi
6
MoO12 (s), respectively. The given uncertainties were calculated as
molybdates along with that of Bi
2
O
3
(s) and MoO (s) was checked in a
3
1
σ of the mean with 0.68 level of confidence.
mixture of triethanolamine and NaOH solution. It was observed that all
the ternary bismuth molybdates, as well as the component oxides were
soluble in the solvent. As mentioned earlier, the maximum time taken
for dissolution was found to be ∼4 min under the chosen experimental
conditions.
2.3. Solution calorimetry
The standard molar enthalpies of formation of bismuth molybdates
were determined by measuring their enthalpies of dissolution. A sui-
table solvent which can dissolve the ternary bismuth molybdates as
The enthalpies of dissolution of the ternary compounds were de-
termined by using an isoperibol calorimeter (Fig. 1) described else-
where [11]. The calorimeter is made from a double walled glass Dewar
of 200 ml capacity with a round bottom and with an evacuated inner
space. The top of the vessel is attached to a Teflon flange by means of a
silicone gasket. This flange is attached to a stainless steel mating cover
using a Viton O-ring. The mating cover has leak tight fittings for in-
troducing a stirrer, sample bulb, heater and a thermistor. Provisions are
given for submerging the entire calorimeter assembly into a water bath.
The temperature of water in the bath is kept constant within ± 0.01 K
which is 1σ of the mean with 0.68 level of confidence. The sample
container is made up of a glass tube of 6 mm outer diameter with a thin
walled bulb blown at the bottom of the tube. Sample is taken in the
glass bulb and a sharp glass push rod is kept to the inner wall of this
well as the component oxides, Bi
2
O
3
(s) and MoO (s) has to be used for
3
the dissolution experiments. Also, the samples should dissolve in the
solvent in a reasonable period of time. Several mineral acids and alkalis
were tried for the solubility experiments and the bismuth molybdates
were found to be insoluble in all of them.
It is known from literature that triethanolamine (TEA) is a versatile
ligand and can readily form coordination complexes with almost all
metal ions and behave as N- and O-donor ligands [7]. TEA can form
3
+
6+
complexes with Bi
and Mo
ions as well. The complexes of TEA
with Bi find its application in medical fields. For the preparation of
medically relevant Bi-TEA complexes, the ratio of Bi to TEA used was
reported to be ranging from 1:2.6 to 1:5.2 [8]. Miller [8] described the
2

P.M. Aiswarya, et al.
Thermochimica Acta xxx (xxxx) xxxx
Fig. 1. A schematic of the solution calorimeter.
Fig. 2. Graphical comparison of XRD patterns of Bi
2
Mo
3
O
12(s): (a) as prepared
Fig. 3. Graphical comparison of XRD patterns of orthorhombic Bi MoO (s): (a)
2
6
compound and b) JCPDS file no.00-021-0103. Small shift of XRD pattern from
as prepared compound and b) JCPDS file no.00-084-0787. Small shift of XRD
the JCPDS pattern is due to the instrumental shift.
pattern from the JCPDS pattern is due to the instrumental shift.
3

P.M. Aiswarya, et al.
Thermochimica Acta xxx (xxxx) xxxx
Table 2
o
a
b
Enthalpy of solution ( sol
H
) of TRIS in 0.10 ± 0.01 mol/kg of HCl solvent
m
b
c
d
(
mass of solvent = 99.52 ± 0.01 g) at 298.15 K and 0.1 MPa .(Molar mass of
−1
TRIS = 121.1 g mol ).
Run
Weight of TRIS
Experimental enthalpy
change (ΔH/J)
Molar enthalpy of solution
d
o
−1
(
w/g)
(
H
/ kJ mol
)
sol
m
1
2
3
4
5
0.2354
0.2313
0.2295
0.2295
0.2161
−57.73
−57.07
−55.71
−56.15
−52.62
−29.70
−29.88
−29.40
−29.63
−29.49
Average: (−29.62 ± 0.37)e
a
b
Tris(hydroxylmethyl) aminomethane (s).
The given uncertainties were calculated as 1σ of the mean with 0.68 level
of confidence.
c
Temperature inside the calorimeter prior to start of experiment was stable
Fig. 4. Graphical comparison of XRD patterns of monoclinic Bi
2
MoO
6
(s): (a) as
within ± 0.001 K which is 1σ of the mean with 0.68 level of confidence.
d
prepared compound and b) JCPDS file no.04-009-3413. Small shift of XRD
Standard uncertainties, u, are u(p) = 0.8 kPa and u(w) = 0.0001 g with
pattern from the JCPDS pattern is due to the instrumental shift.
0.68 level of confidence.
e
o
Expanded uncertainty U( sol
H
), is calculated as 2σ of the mean with 0.95
m
level of confidence. Uncertainty from calibration was also included into the
final uncertainty of the dissolution enthalpies.
Table 3
Experimentally determined values of enthalpies of dissolution (ΔH) and molar
o
enthalpies of dissolution ( sol
H
) of Bi
2
O
3
(s) and MoO
3
(s) in a mixture of
m
a
a
−1
a
(
100.0 ± 0.2 ) ml of (3.00 ± 0.06 ) mol kg NaOH and (25.0 ± 0.1 ) ml of
b
c
triethanolamine at 298.15 K and 0.1 MPa .
Sample
Weight
Experimental
Molar enthalpy of
of
enthalpy
solution
o
/kJ mol−1
)
sample
change (ΔH/J)
(
H
sol
m
c
(
w/g)
Bi
2
O
3
(s)
0.6923
0.4020
0.4400
−62.34
−36.97
−39.84
−41.00
−24.52
−33.37
−18.87
−28.30
−23.45
−41.96
−42.85
−42.19
−43.54
−43.11
−42.66
−43.92
−41.84
−42.55
(
molar
mass = 465.957 g mol−1)
0
.4388
Fig. 5. Graphical comparison of XRD patterns of Bi
6
Mo
2
O
15(s): (a) as prepared
0.2650
0
0
0
0
.3645
.2002
.3152
.2568
compound and b) JCPDS file no.04-018-9896. Small shift of XRD pattern from
the JCPDS pattern is due to the instrumental shift.
Average: (−42.74 ± 1.40)d
MoO
3
(s)
0.3239
0.2459
0.2699
−178.67
−136.19
−150.62
−131.89
−136.71
−79.40
−79.72
(
molar
mass = 143.947 gmol−1)
−80.33
0
0
.2392
.2450
−79.37
−80.32
Average: (−79.83 ± 0.95)d
a
The given uncertainties were calculated as 1σ of the mean with 0.68 level
of confidence.
b
Temperature inside the calorimeter prior to start of experiment was stable
within ± 0.001 K which is 1σ of the mean with 0.68 level of confidence.
c
d
Standard uncertainties, u, are u(p) = 0.8 kPa and u(w) = 0.0001 g.
o
Expanded uncertainty U( sol
H ), is calculated as 2σ of the mean with 0.95
m
level of confidence. Uncertainty from calibration was also included into the
final uncertainty of the dissolution enthalpies.
Fig. 6. Graphical comparison of XRD patterns of Bi
compound and b) XRD data traced from the figure reported by Bleijenberg et al
8]. Small shift of XRD pattern from the JCPDS pattern is due to the instru-
mental shift.
6
MoO12(s): (a) as prepared
sample tube using an O-ring. A stirrer, made of teflon and driven by a
motor, is provided for the uniform stirring of the calorimetric solvent in
the Dewar. The speed of the stirrer is controlled by means of a regulator
and kept constant during the entire period of the experiment.
[
4

P.M. Aiswarya, et al.
Thermochimica Acta xxx (xxxx) xxxx
Table 4
The chemical calibration of the calorimeter was carried out using
tris(hydroxyl methyl) aminomethane (s) (TRIS) (≥0.998 mass fraction
purity, M/s Merck, UK). The calorimetric solvent used for this cali-
bration was 0.1 mol/kg HCl. The sample required for the calibration
was accurately weighed and transferred into the sample bulb. 100 ml of
the calorimetric solvent was taken inside the Dewar flask. The sample
bulb along with the other components was allowed to equilibrate at the
bath temperature. A steady temperature signal was obtained once the
calorimeter attained thermal equilibrium with the surrounding water
bath. The sample bulb was then broken by pushing the glass rod and the
sample was allowed to dissolve in the calorimetric solvent. The con-
sequent variation in the temperature signal was monitored. Electrical
calibration was performed in-situ before and after each of these ex-
periments. The experimental results obtained for the enthalpy of dis-
Experimentally determined values of enthalpies of dissolution (ΔH) and molar
o
enthalpies of dissolution ( sol
H
) of Bi
2
Mo
15 (s) and Bi
100.0 ± 0.2 ) ml of (3.00 ± 0.06 ) mol kg NaOH and (25.0 ± 0.1 ) ml of
triethanolamine at 298.15 K and 0.1 MPa .
3
O12 (s), orthorhombic Bi
2
MoO
6
(s),
m
monoclinic Bi
2
MoO
6
(s), Bi
6
Mo
2
O
6
MoO12 (s) in a mixture of
a
a
−1
a
(
b
c
Sample
Weight of
Experimental
enthalpy change
ΔH (J)
Molar
sample
enthalpy of
solution
c
(
w/g)
o
sol Hm
kJ mol−1)
(
Bi
2
Mo
3
O
12(s)
0.4921
0.5156
0.5338
−94.11
−99.64
−103.83
−102.63
−103.81
−171.70
−173.50
−174.63
−172.55
−171.26
(
molar
mass = 897.798 g mol−1)
0
0
.5340
.5442
solution of TRIS (s) are given in Table 2. The molar enthalpy of solution
Average: (-172.73 ± 2.73)d
−1
of TRIS (s) obtained in the present work is (−29.62 ± 0.37) kJ mol
.
Orthorhombic
Bi MoO (s)
0.3043
0.2758
0.2392
0.2204
−15.76
−31.59
−32.53
−30.44
−30.14
−31.71
The given uncertainties were calculated as 2σ of the mean with 0.95
level of confidence. The obtained value is in good agreement with the
2
6
−14.71
−11.94
−10.89
−15.35
(
molar
−1
mass = 609.904 g mol−1)
reported value of (−29.770 ± 0.032) kJ mol [13]. The uncertainty
given in the reported value is 2σ of the mean with 0.95 level of con-
fidence [13]. These data ensures the suitability of the experimental set
up for calorimetric measurements.
0
.2952
Average: (−31.28 ± 1.96)d
Monoclinic Bi
2
MoO
6
(s)
0.4308
0.3217
0.3745
−38.62
−54.68
−52.06
−51.41
−51.90
−53.64
−53.04
(
molar
−27.46
−31.57
−27.57
−41.13
−47.12
mass = 609.904 g mol−1)
Similar experiments were performed with samples of ternary bis-
muth molybdates as well as with the binary oxides viz., Bi
2
O (s) and
3
0
0
0
.3240
.4677
.5418
MoO
3
(s). In each case, the calorimetric solvent used was a mixture of
−1
1
00 ml of 3 mol kg NaOH and 25 ml of triethanolamine. The volume
Average: (−52.79 ± 2.46)d
of triethanolamine was chosen in such a way that the molar ratio of
metals to triethanolamine was maintained at ∼1:80 for the dissolution
experiments. The current and duration of its passage for the in-situ
electrical calibration were decided by the time taken for the sample to
dissolve completely under the experimental conditions and the weight
of the sample taken for each experiment. The maximum time taken for
the dissolution of the samples was around 4 min. The temperature
changes, (ΔT), during the experiments with TRIS as well as with all the
samples were also corrected for the heat exchange between calorimeter
and surroundings and were used for the evaluation of the enthalpy
changes for the reactions. Calorimetric measurements were repeated
several times to obtain the reproducible data.
Bi
6
Mo
2
O15 (s)
0.3892
0.3556
0.1739
−32.11
−139.08
−140.70
−145.99
−147.42
−146.03
(
molar
−29.68
−15.06
−38.96
−24.55
mass = 1685.765 g mol−1)
0
0
.4455
.2834
Average: (−143.84 ± 7.40)d
Bi
6
MoO12 (s)
0.2653
0.3770
0.2108
−10.25
−59.57
−60.49
−60.63
−60.88
−59.09
(
molar
−14.79
−8.29
mass = 1541.818 g mol−1)
0
0
.4186
.4363
−16.53
−16.72
Average: (−60.13 ± 1.53)d
a
The given uncertainties were calculated as 1σ of the mean with 0.68 level
of confidence.
b
Temperature inside the calorimeter prior to start of experiment was stable
3. Results and discussion
within ± 0.001 K which is 1σ of the mean with 0.68 level of confidence.
c
d
Standard uncertainties, u, are u(p) = 0.8 kPa and u(w) = 0.0001 g.
The experimental results obtained for the enthalpy of solution of the
o
Expanded uncertainty U( sol
H ), is calculated as 2σ of the mean with 0.95
m
starting components Bi
2
O
3
(s) and MoO (s) and those obtained for
3
level of confidence. Uncertainty from calibration was also included into the
final uncertainty of the dissolution enthalpies.
ternary compounds are given in Tables 3 and 4, respectively. The molar
°
enthalpies of solution, sol H of Bi
2
O
3
(s), MoO
3
(s), Bi
2
Mo
3
O
12 (s),
m
orthorhombic-Bi
2
MoO
6
(s), monoclinic-Bi
2
MoO
6
(s), Bi
6
Mo
2
O
15 (s),
The calorimeter was calibrated electrically. The heater used for
electrical calibration was made up of a teflon coated manganin wire
which has a very low temperature coefficient of resistance so that the
change of resistance would be negligible during the calibration. The
resistance of the heater used was 17.425 ± 0.005 Ω which is 1σ of the
mean with 0.68 level of confidence. The heater was immersed in sili-
cone oil taken in a glass tube to enable the conduction of heat from the
heater to the calorimetric solvent. The electrical calibration was per-
formed by applying a constant current through the manganin wire
using a stable power source for a known period of time. The current was
measured using a precision resistor connected in series. The tempera-
ture was measured using a thermistor (M/s Toshniwal Brothers Delhi
Private Limited, Bangalore, India) connected to a data acquisition
system, interfaced to a personal computer and was recorded as a
function of time. The temperature change, ΔT, was corrected for heat
exchange between calorimeter and surroundings by the method sug-
gested by Kubachewski et al [12].
and Bi
6
MoO12 (s), obtained are (−42.74 ± 1.40), (−79.83 ± 0.95),
(
(
−172.72 ± 2.73),
(−31.28 ± 1.96),
(−52.79 ± 2.46),
−1
−143.84 ± 7.40) and (−60.13 ± 1.53) kJ mol , respectively. The
given uncertainties were calculated as 2σ of the mean with 0.95 level of
confidence. The molar enthalpy of formation of the ternary compounds
from the component elements was then obtained by considering sui-
table thermochemical reaction schemes presented in Tables 5. For the
calculation of enthalpies of formation from elements, values of en-
thalpies of formation of the binary oxides were taken from references
[
12,14]. The experimentally determined enthalpies of formation from
°
elements,
f H
2
,
for Bi
2
Mo
3
O
12 (s), orthorhombic Bi
2
MoO
6
(s),
2
98
monoclinic Bi
MoO
6
(s), Bi
6
Mo
2
O
15 (s) and Bi MoO12 (s), respectively
6
are compared with the data calculated from their component oxides by
additive rule in Table 6. It can be seen from the table that the measured
enthalpy of formation of the compounds are higher in the range from
∼
4 to 7% from the data calculated from their component oxides by
additive rule.
5

P.M. Aiswarya, et al.
Thermochimica Acta xxx (xxxx) xxxx
Table 5
Thermodynamic reaction schemes for obtaining the enthalpies of formation from oxides and elements for bismuth molybdates at T = 298.15 K and 0.1 MPab
a
(
s = solid, soln = aqueous solution, g = gas).
o
S. No.
Reaction
ΔH
i
Enthalpies, ΔH
kJ mol
Reference
−
1
(
)
c
c
1
2
3
4
5
Bi
2
O
3
3
(s) + TEA-NaOH (soln) = 2 Bi-complex (soln)
(s) + TEA-NaOH (soln) = Mo-complex (soln)
ΔH
ΔH
ΔH
ΔH
ΔH
1
2
3
4
5
−42.74 ± 1.40
−79.83 ± 0.95
This work
This work
[6]
MoO
d
2 Bi (s) + 3/2 O
Mo (s) + 3/2 O
Bi Mo 12 (s) + TEA-NaOH (soln)
(2 Bi-complex+ 3 Mo-complex) (soln)
2 Bi (s) + 3 Mo (s) + 6 O (g) = Bi Mo
Orthorhombic Bi MoO
(2 Bi-complex+ Mo-complex) (soln)
2 Bi (s) + Mo (s) + 3 O (g) = Orthorhombic Bi
Monoclinic Bi MoO (s) + TEA-NaOH (soln)
(2 Bi-complex+ Mo-complex) (soln)
2 Bi (s) + Mo (s) + 3 O (g) = Monoclinic Bi
Bi Mo 15 (s) + TEA-NaOH (soln)
(6 Bi-complex+ 2 Mo-complex) (soln)
(g) = Bi
MoO12 (s) + TEA-NaOH (soln)
(6 Bi-complex+ Mo-complex) (soln)
(g) = Bi MoO12 (s)
2
(g) = Bi
O
2 3
(s)
−570.7 ± 3.3
d
2
(g) = MoO
3
(s)
−745.2 ± 0.4
[14]
c
2
=
3
O
−172.73 ± 2.73
This work
e
c
6
7
2
2
3
O
12 (s)
ΔH
6
7
= ΔH
= ΔH
1
1
+ 3ΔH
2
+ ΔH
3
+ 3ΔH
4
– ΔH
5
−2915.8 ± 8.2
This work
This work
2
6
(s) + TEA-NaOH (soln)
ΔH
−31.28 ± 1.96
=
e
c
8
9
2
2
MoO
6
(s)
ΔH
8
9
+ ΔH
2
+ ΔH
3
+ ΔH
4
– ΔH
7
−1407.2 ± 7.1
This work
This work
2
6
ΔH
−52.79 ± 2.46
=
1
1
0
1
2
2
MoO
6
(s)
ΔH10 = ΔH
1
+ ΔH
2
+ ΔH
3
+ ΔH
4
– ΔH
9
−1385.7 ± 7.3e
−143.84 ± 7.40
This work
This work
c
e
6
=
2
O
ΔH11
1
1
2
3
6 Bi (s) + 2 Mo (s) + 15/2 O
2
6
Mo
2
O
15 (s)
ΔH12 = 3ΔH
ΔH13
1
+ 2ΔH
2
+ 3ΔH
3
+ 2ΔH
4
– ΔH11
−3346.5 ± 21.7
This work
This work
c
Bi
6
=
−60.13 ± 1.53
1
4
6 Bi (s) + Mo (s) + 6 O
2
6
ΔH14 = 3ΔH
1
+ ΔH
2
+ 3ΔH
3
+ ΔH
4
– ΔH13
−2605.2 ± 20.3e
This work
a
b
c
d
e
Temperature of the calorimeter prior to the actual experiment was stable within ± 0.001 K which is 1σ of the mean with 0.68 level of confidence.
Standard uncertainties, u, are u(p) = 0.8 kPa.
Expanded uncertainties, U (ΔH) are calculated as 2σ of the mean and are at the 0.95 confidence level.
c
Reported uncertainty 1σ of the mean and are at the 0.68 confidence level.
Combined expanded uncertainties, U (ΔH) are calculated as 2σ of the mean and are at the 0.95 confidence level.
c
Table 6
the authors (PMA) acknowledges Department of Atomic Energy, India,
for providing the financial support.
Comparison of experimental enthalpy of formation of compounds with the data
b
calculated by additive rule. The measurements are made at 0.1MPa. .
No
Compound
f H298(kJ mol−1)
°
f H298(kJ mol−1)
°
Difference
References
a
a
(%)
Experimental
Additive rule
[
[
[
1] J. Zhang, N. Li, Review of the studies on fundamental issues in LBE corrosion, J.
Nucl. Mater. 373 (2008) 351–377.
1
2
Bi
2
2
Mo
3
O
12
−2915.8 ± 8.2
−1407.2 ± 7.1
−2806.3 ± 7.0
−1315.9 ± 6.6
3.9
6.9
2] N. Li, Active control of oxygen in molten lead-bismuth eutectic systems to prevent
steel corrosion and coolant contamination, J. Nucl. Mater. 300 (2002) 73–81.
3] P.M. Aiswarya, R. Ganesan, R. Rajamadhavan, T. Gnanasekaran, Partial phase
Bi
MoO
6
orthorhombic
3
Bi
2
MoO
6
−1385.7 ± 7.3
−1315.9 ± 6.6
5.3
diagram of MoO
3
rich section of the ternary Bi-Mo-O system, J. Alloys. Compd. 745
monoclinic
(
2018) 744–752.
4
5
Bi
6
6
Mo
2
O
15
−3346.5 ± 21.7
−2605.2 ± 20.3
−3202.5 ± 19.9
−2457.3 ± 19.8
4.5
6.0
[
4] P.M. Aiswarya, Sajal Ghosh, R. Ganesan, T. Gnanasekaran, Phase diagram studies
on ternary Bi-Mo-O system, Unpublished results. [5] PDF-4+ database-2013,
International Centre for Diffraction Data, USA.
Bi
MoO12
a
Combined expanded uncertainties, U
c
(ΔH) are calculated at the 0.95 con-
[5] PDF-4+ database-2013, International Centre for Diffraction Data, USA.
fidence level.
[6] A.C.A.M. Bleijenberg, B.C. Lippens, G.C.A. Schuit, Catalytic oxidation of 1-Butene
b
2 3 3
over bismuth molybdate catalysts: the system Bi O -MoO , J. Catal. 4 (1965)
Standard uncertainties, u, are u(p) = 0.8 kPa.
. Conclusions
5
81–585.
[
7] K. Majid, R. Mushtaq, S. Ahmad, Syntheis, characterization and coordinating be-
havior of aminoalcohol complexes with transition metals, Euro. J. Chem. 5 (2008)
4
9
69–979.
[
8] W.T. Miller, Some complex sodium bismuth salts of triethanolamine and triiso-
propanolamine, J. Am. Chem. Soc. 62 (1940) 2707–2709.
The standard molar enthalpies of formation of the ternary bismuth
molybdates namely, Bi
2
Mo
Mo
3
O
12 (s), Bi
2
6
MoO
6
(orthorhombic and
[9] R.D. Hancock, I. Cukrowski, J. Baloyi, J. Mashishi, The affinity of bismuth (III) for
nitrogen donor ligands, J. Chem. Soc. Dalton Trans. (1993) 2895–2899.
10] G. Szalontai, G. Kiss, L. Bartha, Equilibria of mononuclear oxomolybdenum (VI)
complexes of triethanolamine- A multinuclear dynamic magnetic resonance study
of structure and exchange mechanisms, Spectrochim. Acta Part A 59 (2003)
1995–2007.
monoclinic phases), Bi
6
2
O
15 (s) and Bi MoO12 (s) from the corre-
[
[
sponding elements were determined by solution calorimetry. The
thermochemical data of these bismuth molybdates are being reported
for the first time.
11] P.M. Aiswarya, R. Ganesan, T. Gnanasekaran, The standard molar enthalpies of
formation and heat capacities of PbMoO
Thermodyn. 116 (2018) 21–31.
4 2 5
(s) and Pb MoO (s), J. Chem.
Acknowledgements
[
[
12] O. Kubachewski, C.B. Alcock, P.J. Spencer, Materials Thermochemistry, 6th ed.,
Pergamon Press, Oxford, 1993.
The authors are thankful to Mr. K. H. Mahendran, Mrs. S.
Premalatha and Mr. J. Prabhakar Rao for the setting up of the solution
calorimeter and interfacing with the computer. The authors are grateful
to Ms. Vaishnavi Krupa and Dr. R. Mythili for their kind help in re-
cording SEM/EDS of the samples. The authors are thankful to Mr. K.
Haridas for making glass bulbs for solution calorimetry work. One of
13] R. Sabbah, A.X. Wu, J.S. Chickos, M.L.P. Leitao, M.V. Roux, L.A. Torres, Reference
materials for calorimetry and differential thermal analysis, Thermochim. Acta 331
(1999) 93–204.
[
14] M.R. Bissengaliyeva, L.P. Ogorodova, M.F. Vigasina, L.V. Melchakova, Enthalpy of
formation of wulfenite, Russ. J. Phys. Chem. A. 87 (2013) 163–165.
6