Fe2(SO4)3 + HI = H2SO4 + I2 + FeSO4

Fe_2(SO_4)_3·xH_2O iron(III) sulfate hydrate + HI hydrogen iodide ⟶ H_2SO_4 sulfuric acid + I_2 iodine + FeSO_4 duretter

Balance the chemical equation algebraically: Fe_2(SO_4)_3·xH_2O + HI ⟶ H_2SO_4 + I_2 + FeSO_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 Fe_2(SO_4)_3·xH_2O + c_2 HI ⟶ c_3 H_2SO_4 + c_4 I_2 + c_5 FeSO_4 Set the number of atoms in the reactants equal to the number of atoms in the products for Fe, O, S, H and I: Fe: | 2 c_1 = c_5 O: | 12 c_1 = 4 c_3 + 4 c_5 S: | 3 c_1 = c_3 + c_5 H: | c_2 = 2 c_3 I: | c_2 = 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 = 2 c_3 = 1 c_4 = 1 c_5 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | Fe_2(SO_4)_3·xH_2O + 2 HI ⟶ H_2SO_4 + I_2 + 2 FeSO_4

+ ⟶ + +

iron(III) sulfate hydrate + hydrogen iodide ⟶ sulfuric acid + iodine + duretter

Construct the equilibrium constant, K, expression for: Fe_2(SO_4)_3·xH_2O + HI ⟶ H_2SO_4 + I_2 + FeSO_4 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: Fe_2(SO_4)_3·xH_2O + 2 HI ⟶ H_2SO_4 + I_2 + 2 FeSO_4 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 Fe_2(SO_4)_3·xH_2O | 1 | -1 HI | 2 | -2 H_2SO_4 | 1 | 1 I_2 | 1 | 1 FeSO_4 | 2 | 2 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression Fe_2(SO_4)_3·xH_2O | 1 | -1 | ([Fe2(SO4)3·xH2O])^(-1) HI | 2 | -2 | ([HI])^(-2) H_2SO_4 | 1 | 1 | [H2SO4] I_2 | 1 | 1 | [I2] FeSO_4 | 2 | 2 | ([FeSO4])^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 = ([Fe2(SO4)3·xH2O])^(-1) ([HI])^(-2) [H2SO4] [I2] ([FeSO4])^2 = ([H2SO4] [I2] ([FeSO4])^2)/([Fe2(SO4)3·xH2O] ([HI])^2)

Construct the rate of reaction expression for: Fe_2(SO_4)_3·xH_2O + HI ⟶ H_2SO_4 + I_2 + FeSO_4 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: Fe_2(SO_4)_3·xH_2O + 2 HI ⟶ H_2SO_4 + I_2 + 2 FeSO_4 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 Fe_2(SO_4)_3·xH_2O | 1 | -1 HI | 2 | -2 H_2SO_4 | 1 | 1 I_2 | 1 | 1 FeSO_4 | 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 Fe_2(SO_4)_3·xH_2O | 1 | -1 | -(Δ[Fe2(SO4)3·xH2O])/(Δt) HI | 2 | -2 | -1/2 (Δ[HI])/(Δt) H_2SO_4 | 1 | 1 | (Δ[H2SO4])/(Δt) I_2 | 1 | 1 | (Δ[I2])/(Δt) FeSO_4 | 2 | 2 | 1/2 (Δ[FeSO4])/(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[Fe2(SO4)3·xH2O])/(Δt) = -1/2 (Δ[HI])/(Δt) = (Δ[H2SO4])/(Δt) = (Δ[I2])/(Δt) = 1/2 (Δ[FeSO4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| iron(III) sulfate hydrate | hydrogen iodide | sulfuric acid | iodine | duretter formula | Fe_2(SO_4)_3·xH_2O | HI | H_2SO_4 | I_2 | FeSO_4 Hill formula | Fe_2O_12S_3 | HI | H_2O_4S | I_2 | FeO_4S name | iron(III) sulfate hydrate | hydrogen iodide | sulfuric acid | iodine | duretter IUPAC name | diferric trisulfate | hydrogen iodide | sulfuric acid | molecular iodine | iron(+2) cation sulfate

| iron(III) sulfate hydrate | hydrogen iodide | sulfuric acid | iodine | duretter molar mass | 399.9 g/mol | 127.912 g/mol | 98.07 g/mol | 253.80894 g/mol | 151.9 g/mol phase | | gas (at STP) | liquid (at STP) | solid (at STP) | melting point | | -50.76 °C | 10.371 °C | 113 °C | boiling point | | -35.55 °C | 279.6 °C | 184 °C | density | | 0.005228 g/cm^3 (at 25 °C) | 1.8305 g/cm^3 | 4.94 g/cm^3 | 2.841 g/cm^3 solubility in water | slightly soluble | very soluble | very soluble | | surface tension | | | 0.0735 N/m | | dynamic viscosity | | 0.001321 Pa s (at -39 °C) | 0.021 Pa s (at 25 °C) | 0.00227 Pa s (at 116 °C) | odor | | | odorless | |