First, free energy data
As in the system at 298 K, only S Î˜ , H 2 S(aq), HS - (aq), S 2 - (aq), SO 4 2 - (aq) and HSO 4 - are thermodynamically stable. The components. The free energy data required to plot the system is listed in the table below.
Table 1 Free energy of each substance in S-H 2 O system 423K
S 2 -
H 2 S(aq)
SO 4 2 -
HSO 4 -
H 2 O(I)
â–³G 423 Î˜ âˆ•kJ
Second, the equilibrium equation
Similar to the previous ones, the equilibrium equations involved here are numbered separately and correspond to the numbers marked on the corresponding balance lines on the dominant area map, but here is the full battery equation.
Third, the analysis of the advantage zone map
The dominant region at 423K is shown in Figure 1 with various sulfur-containing substances and H 2 S(aq) activity of 10 -1 molâˆ•L. Compared with 298K, there are two points worth noting. First, HSO 4 at higher temperatures - the predominant higher pH region extending direction - than the SO 4 2. Second, the stable zone of 423K elemental sulfur is much smaller than at 298K. The equilibrium formula (f) representing the boundary between HS - and S is not important even at 10 -1 mol âˆ•L at 298 K, but the advantage of sulfur at higher temperatures and lower sulfur-containing activity. The zone is determined by the equilibrium formula (c): HSO 4 - -S, equilibrium formula (d): SO 4 2 - -S and equilibrium formula (e): H 2 S(aq)-S. At a certain temperature, as the activity of HSO 4 - or SO 4 2 - decreases, the equilibrium E value falls to a lower value. However, as the H 2 S(aq) activity decreases, the equilibrium E value increases. At a certain temperature and activity of a group of dissolved materials, the elemental sulfur is thermodynamically unstable when the H 2 S(aq)-S line rises above the SO 4 2 - or HSO 4 - line. The ratio of HSO 4 - to SO 4 2 - is limited by the pH of the solution, and the activity of total sulfate and H 2 S (aq) can be independently regulated.
Figure 1 S-H 2 O dominant area map
(423K, S and H 2 O activity is 10 -1 )
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