HCl + KI + KClO3 = H2O + I2 + KCl

HCl hydrogen chloride + KI potassium iodide + KClO_3 potassium chlorate ⟶ H_2O water + I_2 iodine + KCl potassium chloride

Balance the chemical equation algebraically: HCl + KI + KClO_3 ⟶ H_2O + I_2 + KCl Add stoichiometric coefficients, c_i, to the reactants and products: c_1 HCl + c_2 KI + c_3 KClO_3 ⟶ c_4 H_2O + c_5 I_2 + c_6 KCl Set the number of atoms in the reactants equal to the number of atoms in the products for Cl, H, I, K and O: Cl: | c_1 + c_3 = c_6 H: | c_1 = 2 c_4 I: | c_2 = 2 c_5 K: | c_2 + c_3 = c_6 O: | 3 c_3 = 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_3 = 1 and solve the system of equations for the remaining coefficients: c_1 = 6 c_2 = 6 c_3 = 1 c_4 = 3 c_5 = 3 c_6 = 7 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 6 HCl + 6 KI + KClO_3 ⟶ 3 H_2O + 3 I_2 + 7 KCl

+ + ⟶ + +

hydrogen chloride + potassium iodide + potassium chlorate ⟶ water + iodine + potassium chloride

| hydrogen chloride | potassium iodide | potassium chlorate | water | iodine | potassium chloride molecular enthalpy | -92.3 kJ/mol | -327.9 kJ/mol | -397.7 kJ/mol | -285.8 kJ/mol | 0 kJ/mol | -436.5 kJ/mol total enthalpy | -553.8 kJ/mol | -1967 kJ/mol | -397.7 kJ/mol | -857.5 kJ/mol | 0 kJ/mol | -3056 kJ/mol | H_initial = -2919 kJ/mol | | | H_final = -3913 kJ/mol | | ΔH_rxn^0 | -3913 kJ/mol - -2919 kJ/mol = -994.1 kJ/mol (exothermic) | | | | |

| hydrogen chloride | potassium iodide | potassium chlorate | water | iodine | potassium chloride molecular free energy | -95.3 kJ/mol | -324.9 kJ/mol | -296.3 kJ/mol | -237.1 kJ/mol | 0 kJ/mol | -408.5 kJ/mol total free energy | -571.8 kJ/mol | -1949 kJ/mol | -296.3 kJ/mol | -711.3 kJ/mol | 0 kJ/mol | -2860 kJ/mol | G_initial = -2818 kJ/mol | | | G_final = -3571 kJ/mol | | ΔG_rxn^0 | -3571 kJ/mol - -2818 kJ/mol = -753.3 kJ/mol (exergonic) | | | | |

Construct the equilibrium constant, K, expression for: HCl + KI + KClO_3 ⟶ H_2O + I_2 + KCl 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: 6 HCl + 6 KI + KClO_3 ⟶ 3 H_2O + 3 I_2 + 7 KCl 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 HCl | 6 | -6 KI | 6 | -6 KClO_3 | 1 | -1 H_2O | 3 | 3 I_2 | 3 | 3 KCl | 7 | 7 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression HCl | 6 | -6 | ([HCl])^(-6) KI | 6 | -6 | ([KI])^(-6) KClO_3 | 1 | -1 | ([KClO3])^(-1) H_2O | 3 | 3 | ([H2O])^3 I_2 | 3 | 3 | ([I2])^3 KCl | 7 | 7 | ([KCl])^7 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 = ([HCl])^(-6) ([KI])^(-6) ([KClO3])^(-1) ([H2O])^3 ([I2])^3 ([KCl])^7 = (([H2O])^3 ([I2])^3 ([KCl])^7)/(([HCl])^6 ([KI])^6 [KClO3])

Construct the rate of reaction expression for: HCl + KI + KClO_3 ⟶ H_2O + I_2 + KCl 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: 6 HCl + 6 KI + KClO_3 ⟶ 3 H_2O + 3 I_2 + 7 KCl 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 HCl | 6 | -6 KI | 6 | -6 KClO_3 | 1 | -1 H_2O | 3 | 3 I_2 | 3 | 3 KCl | 7 | 7 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 HCl | 6 | -6 | -1/6 (Δ[HCl])/(Δt) KI | 6 | -6 | -1/6 (Δ[KI])/(Δt) KClO_3 | 1 | -1 | -(Δ[KClO3])/(Δt) H_2O | 3 | 3 | 1/3 (Δ[H2O])/(Δt) I_2 | 3 | 3 | 1/3 (Δ[I2])/(Δt) KCl | 7 | 7 | 1/7 (Δ[KCl])/(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 = -1/6 (Δ[HCl])/(Δt) = -1/6 (Δ[KI])/(Δt) = -(Δ[KClO3])/(Δt) = 1/3 (Δ[H2O])/(Δt) = 1/3 (Δ[I2])/(Δt) = 1/7 (Δ[KCl])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| hydrogen chloride | potassium iodide | potassium chlorate | water | iodine | potassium chloride formula | HCl | KI | KClO_3 | H_2O | I_2 | KCl Hill formula | ClH | IK | ClKO_3 | H_2O | I_2 | ClK name | hydrogen chloride | potassium iodide | potassium chlorate | water | iodine | potassium chloride IUPAC name | hydrogen chloride | potassium iodide | potassium chlorate | water | molecular iodine | potassium chloride