A.Mesophilic aerobic respiration of glucose (C6H12O6) in a freshwater ecosystem

1. Glucose(aq) + 6O2(aq) = 6CO2(aq) + 6H2O(A)

2. 25 °C, I = 0.01 m, pH 7, [glucose] = 1 μm, dissolved oxygen and dissolved inorganic carbon (DIC) at saturation with the atmosphere ([O2] = 259 μm, [DIC] = [CO2] + [HCO3 −] = 220 μm).

3. Considering CO2(aq) + H2O = H+ + HCO3 −, with $\Delta G_r^0$ = 36.22 kJ/mol and the corresponding equilibrium constant (K r) equal to 4.51 × 10−7, then $a_{{\mathrm{CO}}_2}$= 0.22 $a_{{\mathrm{HCO}}_3^{-}}$.

4. Activity coefficients (γ) from Table 1 for glucose (1.00), O2 (1.00), CO2 (1.00).

5. Using thermodynamic data at 25 °C, $\Delta G_A^0$ is −2922.3 kJ/mol. Using Equations 5, 7, and parameters given in Steps 2–4, QA is 0.884. ΔGA calculated with Equation (1) is then −2917.6 kJ/mol.

B. Psychrophilic anaerobic respiration (with sulphate) of acetate in marine sediments

1. CH3COO− + SO4 2− = 2HCO3 − + HS−(B)

2. 10 °C, I = 0.7 m, pH 8.1, [total sulphate] = 28 mm, [total acetate] = [DIC] = 10 mm, [total sulphide] = 1 μm.

3. At these conditions, [SO4 2−] = 18.1mm, [CH3COO−] = 7.7 mm, [HCO3 −] = 6.1 mm, [HS−] ≈ [total sulphide].

4. Activity coefficients (γ) from Table 1 for SO4 2− (0.16), acetate− (0.66), HCO3 − (0.66), HS− (0.66).

5. Using thermodynamic data at 10 °C, $\Delta G_B^0$ is −45.8 kJ/mol. Using Equations 5, 7, and parameters given in Steps 2–4, QB is 10–6.13. ΔGB calculated with Equation (1) is then equal to −79.0 kJ/mol.

C. Thermophilic methanogenesis in a 2‐phase (gas + aqueous) laboratory experiment

1. CO2(g) + 4H2(g) = CH4(aq) + 2H2O(C)

2. 85 °C, I = 0.01 m, pH 6.5, $P_{{\mathrm{CO}}_2}$ = 0.2 bar, $P_{{\mathrm{H}}_2}$ = 0.8 bar, [CH4] = 1 μm.

3. If $P_{{\mathrm{CO}}_2}$ and $P_{{\mathrm{H}}_2}$ are maintained at 0.2 bar and 0.8 bar, respectively, speciation calculations are not necessary.

4. Fugacity coefficients (λ) for CO2 (1.00) and H2 (1.00) and activity coefficient (γ) for CH4 (1.00) interpolated from information in Table 1.

5. Using thermodynamic data at 85 °C, $\Delta G_C^0$ is −85.2 kJ/mol. Using Equations 5, 7 and parameters given in Steps 2–4, QC is 10–4.91. ΔGC calculated with Equation (1) is then equal to −118.9 kJ/mol.

D. Mesophilic anaerobic ammonia oxidation (anammox) in a wastewater reactor

1. NH4 + + NO2 − = N2(g) + 2H2O(D)

2. 36°C, I = 0.5 m, pH 7, [total ammonia] = 7.1 mm, [total nitrite] = 1.8 mm, $P_{N_2}$ = 0.1 bar.

3. At these conditions, [NH4 +] ≈ [total ammonia], [NO2 −] ≈ [total nitrite].

4. Activity coefficients (γ) for NH4 + (0.69) and NO2 − (0.69) and fugacity coefficient (λ) for N2 (1.00) interpolated from information in Table 1.

5. Using thermodynamic data at 36 °C, $\Delta G_D^0$ is −364.2 kJ/mol. Using Equations 5, 7 and parameters given in Steps 2–4, QD is 104.26. ΔGD calculated with Equation (1) is then equal to −339.3 kJ/mol.

E. Mesophilic aerobic pyrite oxidation in acid mine drainage

1. FeS2(py) + 3.5O2(g) + H2O = Fe2+ + 2HSO4 −(E)

2. 25 °C, I = 0.5 m, pH 1, dissolved oxygen at saturation with the atmosphere ([O2] = 259 μm), [Fe2+] = 0.026 μm, [HSO4 −] = 0.149 μm.

3. Considering HSO4 − = H+ + SO4 2−, with $\Delta G_r^0$ = 11.30 kJ/mol and the corresponding equilibrium constant (K r) equal to 1.05 × 10−2, then $a_{{\mathrm{HSO}}_4^{-}}$ = 9.55 $a_{{\mathrm{SO}}_4^{2-}}$.

4. Activity coefficients (γ) for Fe2+ (0.28), HSO4 − (0.67) and fugacity coefficient (λ) for O2 (1.00) interpolated from information in Table 1.

5. Using thermodynamic data at 25 °C, $\Delta G_E^0$ is −1205.6 kJ/mol. Using Equations 5, 7 and parameters given in Steps 2–4, QE is 108.41. ΔGE calculated with Equation (1) is then equal to −1157.7 kJ/mol.