KI + Fe2(SO4)3 = K2SO4 + I2 + FeSO4

KI (potassium iodide) + Fe_2(SO_4)_3·xH_2O (iron(III) sulfate hydrate) ⟶ K_2SO_4 (potassium sulfate) + I_2 (iodine) + FeSO_4 (duretter)

Balance the chemical equation algebraically: KI + Fe_2(SO_4)_3·xH_2O ⟶ K_2SO_4 + I_2 + FeSO_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 KI + c_2 Fe_2(SO_4)_3·xH_2O ⟶ c_3 K_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 I, K, Fe, O and S: I: | c_1 = 2 c_4 K: | c_1 = 2 c_3 Fe: | 2 c_2 = c_5 O: | 12 c_2 = 4 c_3 + 4 c_5 S: | 3 c_2 = c_3 + 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_2 = 1 and solve the system of equations for the remaining coefficients: c_1 = 2 c_2 = 1 c_3 = 1 c_4 = 1 c_5 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 KI + Fe_2(SO_4)_3·xH_2O ⟶ K_2SO_4 + I_2 + 2 FeSO_4

+ ⟶ + +

potassium iodide + iron(III) sulfate hydrate ⟶ potassium sulfate + iodine + duretter

Construct the equilibrium constant, K, expression for: KI + Fe_2(SO_4)_3·xH_2O ⟶ K_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: 2 KI + Fe_2(SO_4)_3·xH_2O ⟶ K_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 KI | 2 | -2 Fe_2(SO_4)_3·xH_2O | 1 | -1 K_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 KI | 2 | -2 | ([KI])^(-2) Fe_2(SO_4)_3·xH_2O | 1 | -1 | ([Fe2(SO4)3·xH2O])^(-1) K_2SO_4 | 1 | 1 | [K2SO4] 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 = ([KI])^(-2) ([Fe2(SO4)3·xH2O])^(-1) [K2SO4] [I2] ([FeSO4])^2 = ([K2SO4] [I2] ([FeSO4])^2)/(([KI])^2 [Fe2(SO4)3·xH2O])

Construct the rate of reaction expression for: KI + Fe_2(SO_4)_3·xH_2O ⟶ K_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: 2 KI + Fe_2(SO_4)_3·xH_2O ⟶ K_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 KI | 2 | -2 Fe_2(SO_4)_3·xH_2O | 1 | -1 K_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 KI | 2 | -2 | -1/2 (Δ[KI])/(Δt) Fe_2(SO_4)_3·xH_2O | 1 | -1 | -(Δ[Fe2(SO4)3·xH2O])/(Δt) K_2SO_4 | 1 | 1 | (Δ[K2SO4])/(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 = -1/2 (Δ[KI])/(Δt) = -(Δ[Fe2(SO4)3·xH2O])/(Δt) = (Δ[K2SO4])/(Δt) = (Δ[I2])/(Δt) = 1/2 (Δ[FeSO4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| potassium iodide | iron(III) sulfate hydrate | potassium sulfate | iodine | duretter formula | KI | Fe_2(SO_4)_3·xH_2O | K_2SO_4 | I_2 | FeSO_4 Hill formula | IK | Fe_2O_12S_3 | K_2O_4S | I_2 | FeO_4S name | potassium iodide | iron(III) sulfate hydrate | potassium sulfate | iodine | duretter IUPAC name | potassium iodide | diferric trisulfate | dipotassium sulfate | molecular iodine | iron(+2) cation sulfate

| potassium iodide | iron(III) sulfate hydrate | potassium sulfate | iodine | duretter molar mass | 166.0028 g/mol | 399.9 g/mol | 174.25 g/mol | 253.80894 g/mol | 151.9 g/mol phase | solid (at STP) | | | solid (at STP) | melting point | 681 °C | | | 113 °C | boiling point | 1330 °C | | | 184 °C | density | 3.123 g/cm^3 | | | 4.94 g/cm^3 | 2.841 g/cm^3 solubility in water | | slightly soluble | soluble | | dynamic viscosity | 0.0010227 Pa s (at 732.9 °C) | | | 0.00227 Pa s (at 116 °C) |