O2 + FeAsS = SO2 + Fe2O3 + As2O3

O_2 oxygen + FeAsS ⟶ SO_2 sulfur dioxide + Fe_2O_3 iron(III) oxide + As_2O_3 arsenic trioxide

Balance the chemical equation algebraically: O_2 + FeAsS ⟶ SO_2 + Fe_2O_3 + As_2O_3 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 O_2 + c_2 FeAsS ⟶ c_3 SO_2 + c_4 Fe_2O_3 + c_5 As_2O_3 Set the number of atoms in the reactants equal to the number of atoms in the products for O, Fe, As and S: O: | 2 c_1 = 2 c_3 + 3 c_4 + 3 c_5 Fe: | c_2 = 2 c_4 As: | c_2 = 2 c_5 S: | c_2 = c_3 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_4 = 1 and solve the system of equations for the remaining coefficients: c_1 = 5 c_2 = 2 c_3 = 2 c_4 = 1 c_5 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 5 O_2 + 2 FeAsS ⟶ 2 SO_2 + Fe_2O_3 + As_2O_3

+ FeAsS ⟶ + +

oxygen + FeAsS ⟶ sulfur dioxide + iron(III) oxide + arsenic trioxide

Construct the equilibrium constant, K, expression for: O_2 + FeAsS ⟶ SO_2 + Fe_2O_3 + As_2O_3 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: 5 O_2 + 2 FeAsS ⟶ 2 SO_2 + Fe_2O_3 + As_2O_3 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 O_2 | 5 | -5 FeAsS | 2 | -2 SO_2 | 2 | 2 Fe_2O_3 | 1 | 1 As_2O_3 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression O_2 | 5 | -5 | ([O2])^(-5) FeAsS | 2 | -2 | ([FeAsS])^(-2) SO_2 | 2 | 2 | ([SO2])^2 Fe_2O_3 | 1 | 1 | [Fe2O3] As_2O_3 | 1 | 1 | [As2O3] 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 = ([O2])^(-5) ([FeAsS])^(-2) ([SO2])^2 [Fe2O3] [As2O3] = (([SO2])^2 [Fe2O3] [As2O3])/(([O2])^5 ([FeAsS])^2)

Construct the rate of reaction expression for: O_2 + FeAsS ⟶ SO_2 + Fe_2O_3 + As_2O_3 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: 5 O_2 + 2 FeAsS ⟶ 2 SO_2 + Fe_2O_3 + As_2O_3 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 O_2 | 5 | -5 FeAsS | 2 | -2 SO_2 | 2 | 2 Fe_2O_3 | 1 | 1 As_2O_3 | 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 O_2 | 5 | -5 | -1/5 (Δ[O2])/(Δt) FeAsS | 2 | -2 | -1/2 (Δ[FeAsS])/(Δt) SO_2 | 2 | 2 | 1/2 (Δ[SO2])/(Δt) Fe_2O_3 | 1 | 1 | (Δ[Fe2O3])/(Δt) As_2O_3 | 1 | 1 | (Δ[As2O3])/(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 = -1/5 (Δ[O2])/(Δt) = -1/2 (Δ[FeAsS])/(Δt) = 1/2 (Δ[SO2])/(Δt) = (Δ[Fe2O3])/(Δt) = (Δ[As2O3])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| oxygen | FeAsS | sulfur dioxide | iron(III) oxide | arsenic trioxide formula | O_2 | FeAsS | SO_2 | Fe_2O_3 | As_2O_3 Hill formula | O_2 | AsFeS | O_2S | Fe_2O_3 | As_2O_3 name | oxygen | | sulfur dioxide | iron(III) oxide | arsenic trioxide IUPAC name | molecular oxygen | | sulfur dioxide | | 2, 4, 5-trioxa-1, 3-diarsabicyclo[1.1.1]pentane

| oxygen | FeAsS | sulfur dioxide | iron(III) oxide | arsenic trioxide molar mass | 31.998 g/mol | 162.83 g/mol | 64.06 g/mol | 159.69 g/mol | 197.84 g/mol phase | gas (at STP) | | gas (at STP) | solid (at STP) | solid (at STP) melting point | -218 °C | | -73 °C | 1565 °C | 312 °C boiling point | -183 °C | | -10 °C | | 465 °C density | 0.001429 g/cm^3 (at 0 °C) | | 0.002619 g/cm^3 (at 25 °C) | 5.26 g/cm^3 | 4.15 g/cm^3 solubility in water | | | | insoluble | surface tension | 0.01347 N/m | | 0.02859 N/m | | dynamic viscosity | 2.055×10^-5 Pa s (at 25 °C) | | 1.282×10^-5 Pa s (at 25 °C) | | odor | odorless | | | odorless |