H2S + FeBr3 = S + HBr + FeBr2

H_2S hydrogen sulfide + FeBr_3 iron(III) bromide ⟶ S mixed sulfur + HBr hydrogen bromide + FeBr_2 iron(II) bromide

Balance the chemical equation algebraically: H_2S + FeBr_3 ⟶ S + HBr + FeBr_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2S + c_2 FeBr_3 ⟶ c_3 S + c_4 HBr + c_5 FeBr_2 Set the number of atoms in the reactants equal to the number of atoms in the products for H, S, Br and Fe: H: | 2 c_1 = c_4 S: | c_1 = c_3 Br: | 3 c_2 = c_4 + 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 = 1 c_4 = 2 c_5 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | H_2S + 2 FeBr_3 ⟶ S + 2 HBr + 2 FeBr_2

+ ⟶ + +

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

Construct the equilibrium constant, K, expression for: H_2S + FeBr_3 ⟶ S + HBr + FeBr_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 FeBr_3 ⟶ S + 2 HBr + 2 FeBr_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 FeBr_3 | 2 | -2 S | 1 | 1 HBr | 2 | 2 FeBr_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) FeBr_3 | 2 | -2 | ([FeBr3])^(-2) S | 1 | 1 | [S] HBr | 2 | 2 | ([HBr])^2 FeBr_2 | 2 | 2 | ([FeBr2])^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) ([FeBr3])^(-2) [S] ([HBr])^2 ([FeBr2])^2 = ([S] ([HBr])^2 ([FeBr2])^2)/([H2S] ([FeBr3])^2)

Construct the rate of reaction expression for: H_2S + FeBr_3 ⟶ S + HBr + FeBr_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 FeBr_3 ⟶ S + 2 HBr + 2 FeBr_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 FeBr_3 | 2 | -2 S | 1 | 1 HBr | 2 | 2 FeBr_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) FeBr_3 | 2 | -2 | -1/2 (Δ[FeBr3])/(Δt) S | 1 | 1 | (Δ[S])/(Δt) HBr | 2 | 2 | 1/2 (Δ[HBr])/(Δt) FeBr_2 | 2 | 2 | 1/2 (Δ[FeBr2])/(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[FeBr3])/(Δt) = (Δ[S])/(Δt) = 1/2 (Δ[HBr])/(Δt) = 1/2 (Δ[FeBr2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| hydrogen sulfide | iron(III) bromide | mixed sulfur | hydrogen bromide | iron(II) bromide formula | H_2S | FeBr_3 | S | HBr | FeBr_2 Hill formula | H_2S | Br_3Fe | S | BrH | Br_2Fe name | hydrogen sulfide | iron(III) bromide | mixed sulfur | hydrogen bromide | iron(II) bromide IUPAC name | hydrogen sulfide | tribromoiron | sulfur | hydrogen bromide | dibromoiron

| hydrogen sulfide | iron(III) bromide | mixed sulfur | hydrogen bromide | iron(II) bromide molar mass | 34.08 g/mol | 295.56 g/mol | 32.06 g/mol | 80.912 g/mol | 215.65 g/mol phase | gas (at STP) | | solid (at STP) | gas (at STP) | solid (at STP) melting point | -85 °C | | 112.8 °C | -86.8 °C | 684 °C boiling point | -60 °C | | 444.7 °C | -66.38 °C | 934 °C density | 0.001393 g/cm^3 (at 25 °C) | | 2.07 g/cm^3 | 0.003307 g/cm^3 (at 25 °C) | 4.63 g/cm^3 solubility in water | | | | miscible | surface tension | | | | 0.0271 N/m | dynamic viscosity | 1.239×10^-5 Pa s (at 25 °C) | | | 8.4×10^-4 Pa s (at -75 °C) | odor | | odorless | | |