H2S + O3 = H2O + SO2

H_2S hydrogen sulfide + O_3 ozone ⟶ H_2O water + SO_2 sulfur dioxide

Balance the chemical equation algebraically: H_2S + O_3 ⟶ H_2O + SO_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2S + c_2 O_3 ⟶ c_3 H_2O + c_4 SO_2 Set the number of atoms in the reactants equal to the number of atoms in the products for H, S and O: H: | 2 c_1 = 2 c_3 S: | c_1 = c_4 O: | 3 c_2 = c_3 + 2 c_4 Since the coefficients are relative quantities and underdetermined, choose a coefficient to set arbitrarily. To keep the coefficients small, the arbitrary value is ordinarily one. For instance, set c_1 = 1 and solve the system of equations for the remaining coefficients: c_1 = 1 c_2 = 1 c_3 = 1 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | H_2S + O_3 ⟶ H_2O + SO_2

+ ⟶ +

hydrogen sulfide + ozone ⟶ water + sulfur dioxide

| hydrogen sulfide | ozone | water | sulfur dioxide molecular enthalpy | -20.6 kJ/mol | 142.7 kJ/mol | -285.8 kJ/mol | -296.8 kJ/mol total enthalpy | -20.6 kJ/mol | 142.7 kJ/mol | -285.8 kJ/mol | -296.8 kJ/mol | H_initial = 122.1 kJ/mol | | H_final = -582.6 kJ/mol | ΔH_rxn^0 | -582.6 kJ/mol - 122.1 kJ/mol = -704.7 kJ/mol (exothermic) | | |

| hydrogen sulfide | ozone | water | sulfur dioxide molecular free energy | -33.4 kJ/mol | 163.2 kJ/mol | -237.1 kJ/mol | -300.1 kJ/mol total free energy | -33.4 kJ/mol | 163.2 kJ/mol | -237.1 kJ/mol | -300.1 kJ/mol | G_initial = 129.8 kJ/mol | | G_final = -537.2 kJ/mol | ΔG_rxn^0 | -537.2 kJ/mol - 129.8 kJ/mol = -667 kJ/mol (exergonic) | | |

| hydrogen sulfide | ozone | water | sulfur dioxide molecular entropy | 206 J/(mol K) | 239 J/(mol K) | 69.91 J/(mol K) | 248 J/(mol K) total entropy | 206 J/(mol K) | 239 J/(mol K) | 69.91 J/(mol K) | 248 J/(mol K) | S_initial = 445 J/(mol K) | | S_final = 317.9 J/(mol K) | ΔS_rxn^0 | 317.9 J/(mol K) - 445 J/(mol K) = -127.1 J/(mol K) (exoentropic) | | |

Construct the equilibrium constant, K, expression for: H_2S + O_3 ⟶ H_2O + SO_2 Plan: • Balance the chemical equation. • Determine the stoichiometric numbers. • Assemble the activity expression for each chemical species. • Use the activity expressions to build the equilibrium constant expression. Write the balanced chemical equation: H_2S + O_3 ⟶ H_2O + SO_2 Assign stoichiometric numbers, ν_i, using the stoichiometric coefficients, c_i, from the balanced chemical equation in the following manner: ν_i = -c_i for reactants and ν_i = c_i for products: chemical species | c_i | ν_i H_2S | 1 | -1 O_3 | 1 | -1 H_2O | 1 | 1 SO_2 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression H_2S | 1 | -1 | ([H2S])^(-1) O_3 | 1 | -1 | ([O3])^(-1) H_2O | 1 | 1 | [H2O] SO_2 | 1 | 1 | [SO2] The equilibrium constant symbol in the concentration basis is: K_c Mulitply the activity expressions to arrive at the K_c expression: Answer: | | K_c = ([H2S])^(-1) ([O3])^(-1) [H2O] [SO2] = ([H2O] [SO2])/([H2S] [O3])

Construct the rate of reaction expression for: H_2S + O_3 ⟶ H_2O + SO_2 Plan: • Balance the chemical equation. • Determine the stoichiometric numbers. • Assemble the rate term for each chemical species. • Write the rate of reaction expression. Write the balanced chemical equation: H_2S + O_3 ⟶ H_2O + SO_2 Assign stoichiometric numbers, ν_i, using the stoichiometric coefficients, c_i, from the balanced chemical equation in the following manner: ν_i = -c_i for reactants and ν_i = c_i for products: chemical species | c_i | ν_i H_2S | 1 | -1 O_3 | 1 | -1 H_2O | 1 | 1 SO_2 | 1 | 1 The rate term for each chemical species, B_i, is 1/ν_i(Δ[B_i])/(Δt) where [B_i] is the amount concentration and t is time: chemical species | c_i | ν_i | rate term H_2S | 1 | -1 | -(Δ[H2S])/(Δt) O_3 | 1 | -1 | -(Δ[O3])/(Δt) H_2O | 1 | 1 | (Δ[H2O])/(Δt) SO_2 | 1 | 1 | (Δ[SO2])/(Δt) (for infinitesimal rate of change, replace Δ with d) Set the rate terms equal to each other to arrive at the rate expression: Answer: | | rate = -(Δ[H2S])/(Δt) = -(Δ[O3])/(Δt) = (Δ[H2O])/(Δt) = (Δ[SO2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| hydrogen sulfide | ozone | water | sulfur dioxide formula | H_2S | O_3 | H_2O | SO_2 Hill formula | H_2S | O_3 | H_2O | O_2S name | hydrogen sulfide | ozone | water | sulfur dioxide