H2S + FeCl3 = HCl + S + FeCl2

H_2S (hydrogen sulfide) + FeCl_3 (iron(III) chloride) ⟶ HCl (hydrogen chloride) + S (mixed sulfur) + FeCl_2 (iron(II) chloride)

Balance the chemical equation algebraically: H_2S + FeCl_3 ⟶ HCl + S + FeCl_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2S + c_2 FeCl_3 ⟶ c_3 HCl + c_4 S + c_5 FeCl_2 Set the number of atoms in the reactants equal to the number of atoms in the products for H, S, Cl and Fe: H: | 2 c_1 = c_3 S: | c_1 = c_4 Cl: | 3 c_2 = c_3 + 2 c_5 Fe: | c_2 = c_5 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 = 2 c_3 = 2 c_4 = 1 c_5 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | H_2S + 2 FeCl_3 ⟶ 2 HCl + S + 2 FeCl_2

+ ⟶ + +

hydrogen sulfide + iron(III) chloride ⟶ hydrogen chloride + mixed sulfur + iron(II) chloride

Construct the equilibrium constant, K, expression for: H_2S + FeCl_3 ⟶ HCl + S + FeCl_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 + 2 FeCl_3 ⟶ 2 HCl + S + 2 FeCl_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 FeCl_3 | 2 | -2 HCl | 2 | 2 S | 1 | 1 FeCl_2 | 2 | 2 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) FeCl_3 | 2 | -2 | ([FeCl3])^(-2) HCl | 2 | 2 | ([HCl])^2 S | 1 | 1 | [S] FeCl_2 | 2 | 2 | ([FeCl2])^2 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) ([FeCl3])^(-2) ([HCl])^2 [S] ([FeCl2])^2 = (([HCl])^2 [S] ([FeCl2])^2)/([H2S] ([FeCl3])^2)

Construct the rate of reaction expression for: H_2S + FeCl_3 ⟶ HCl + S + FeCl_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 + 2 FeCl_3 ⟶ 2 HCl + S + 2 FeCl_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 FeCl_3 | 2 | -2 HCl | 2 | 2 S | 1 | 1 FeCl_2 | 2 | 2 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) FeCl_3 | 2 | -2 | -1/2 (Δ[FeCl3])/(Δt) HCl | 2 | 2 | 1/2 (Δ[HCl])/(Δt) S | 1 | 1 | (Δ[S])/(Δt) FeCl_2 | 2 | 2 | 1/2 (Δ[FeCl2])/(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) = -1/2 (Δ[FeCl3])/(Δt) = 1/2 (Δ[HCl])/(Δt) = (Δ[S])/(Δt) = 1/2 (Δ[FeCl2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| hydrogen sulfide | iron(III) chloride | hydrogen chloride | mixed sulfur | iron(II) chloride formula | H_2S | FeCl_3 | HCl | S | FeCl_2 Hill formula | H_2S | Cl_3Fe | ClH | S | Cl_2Fe name | hydrogen sulfide | iron(III) chloride | hydrogen chloride | mixed sulfur | iron(II) chloride IUPAC name | hydrogen sulfide | trichloroiron | hydrogen chloride | sulfur | dichloroiron

| hydrogen sulfide | iron(III) chloride | hydrogen chloride | mixed sulfur | iron(II) chloride molar mass | 34.08 g/mol | 162.2 g/mol | 36.46 g/mol | 32.06 g/mol | 126.7 g/mol phase | gas (at STP) | solid (at STP) | gas (at STP) | solid (at STP) | solid (at STP) melting point | -85 °C | 304 °C | -114.17 °C | 112.8 °C | 677 °C boiling point | -60 °C | | -85 °C | 444.7 °C | density | 0.001393 g/cm^3 (at 25 °C) | | 0.00149 g/cm^3 (at 25 °C) | 2.07 g/cm^3 | 3.16 g/cm^3 solubility in water | | | miscible | | dynamic viscosity | 1.239×10^-5 Pa s (at 25 °C) | | | |