KI + SO3 = I2 + K2SO3

KI potassium iodide + SO_3 sulfur trioxide ⟶ I_2 iodine + K_2SO_3 potassium sulfite

Balance the chemical equation algebraically: KI + SO_3 ⟶ I_2 + K_2SO_3 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 KI + c_2 SO_3 ⟶ c_3 I_2 + c_4 K_2SO_3 Set the number of atoms in the reactants equal to the number of atoms in the products for I, K, O and S: I: | c_1 = 2 c_3 K: | c_1 = 2 c_4 O: | 3 c_2 = 3 c_4 S: | c_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_2 = 1 and solve the system of equations for the remaining coefficients: c_1 = 2 c_2 = 1 c_3 = 1 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 KI + SO_3 ⟶ I_2 + K_2SO_3

+ ⟶ +

potassium iodide + sulfur trioxide ⟶ iodine + potassium sulfite

Construct the equilibrium constant, K, expression for: KI + SO_3 ⟶ I_2 + K_2SO_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: 2 KI + SO_3 ⟶ I_2 + K_2SO_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 KI | 2 | -2 SO_3 | 1 | -1 I_2 | 1 | 1 K_2SO_3 | 1 | 1 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) SO_3 | 1 | -1 | ([SO3])^(-1) I_2 | 1 | 1 | [I2] K_2SO_3 | 1 | 1 | [K2SO3] 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) ([SO3])^(-1) [I2] [K2SO3] = ([I2] [K2SO3])/(([KI])^2 [SO3])

Construct the rate of reaction expression for: KI + SO_3 ⟶ I_2 + K_2SO_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: 2 KI + SO_3 ⟶ I_2 + K_2SO_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 KI | 2 | -2 SO_3 | 1 | -1 I_2 | 1 | 1 K_2SO_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 KI | 2 | -2 | -1/2 (Δ[KI])/(Δt) SO_3 | 1 | -1 | -(Δ[SO3])/(Δt) I_2 | 1 | 1 | (Δ[I2])/(Δt) K_2SO_3 | 1 | 1 | (Δ[K2SO3])/(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[SO3])/(Δt) = (Δ[I2])/(Δt) = (Δ[K2SO3])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| potassium iodide | sulfur trioxide | iodine | potassium sulfite formula | KI | SO_3 | I_2 | K_2SO_3 Hill formula | IK | O_3S | I_2 | K_2O_3S name | potassium iodide | sulfur trioxide | iodine | potassium sulfite IUPAC name | potassium iodide | sulfur trioxide | molecular iodine | dipotassium sulfite

| potassium iodide | sulfur trioxide | iodine | potassium sulfite molar mass | 166.0028 g/mol | 80.06 g/mol | 253.80894 g/mol | 158.25 g/mol phase | solid (at STP) | liquid (at STP) | solid (at STP) | melting point | 681 °C | 16.8 °C | 113 °C | boiling point | 1330 °C | 44.7 °C | 184 °C | density | 3.123 g/cm^3 | 1.97 g/cm^3 | 4.94 g/cm^3 | solubility in water | | reacts | | dynamic viscosity | 0.0010227 Pa s (at 732.9 °C) | 0.00159 Pa s (at 30 °C) | 0.00227 Pa s (at 116 °C) |