H2O + NaI + NaIO3 = NaOH + I2

H_2O water + NaI sodium iodide + NaIO_3 sodium iodate ⟶ NaOH sodium hydroxide + I_2 iodine

Balance the chemical equation algebraically: H_2O + NaI + NaIO_3 ⟶ NaOH + I_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2O + c_2 NaI + c_3 NaIO_3 ⟶ c_4 NaOH + c_5 I_2 Set the number of atoms in the reactants equal to the number of atoms in the products for H, O, I and Na: H: | 2 c_1 = c_4 O: | c_1 + 3 c_3 = c_4 I: | c_2 + c_3 = 2 c_5 Na: | c_2 + 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 = 3 c_2 = 5 c_3 = 1 c_4 = 6 c_5 = 3 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 3 H_2O + 5 NaI + NaIO_3 ⟶ 6 NaOH + 3 I_2

+ + ⟶ +

water + sodium iodide + sodium iodate ⟶ sodium hydroxide + iodine

| water | sodium iodide | sodium iodate | sodium hydroxide | iodine molecular enthalpy | -285.8 kJ/mol | -287.8 kJ/mol | -481.8 kJ/mol | -425.8 kJ/mol | 0 kJ/mol total enthalpy | -857.5 kJ/mol | -1439 kJ/mol | -481.8 kJ/mol | -2555 kJ/mol | 0 kJ/mol | H_initial = -2778 kJ/mol | | | H_final = -2555 kJ/mol | ΔH_rxn^0 | -2555 kJ/mol - -2778 kJ/mol = 223.5 kJ/mol (endothermic) | | | |

Construct the equilibrium constant, K, expression for: H_2O + NaI + NaIO_3 ⟶ NaOH + I_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: 3 H_2O + 5 NaI + NaIO_3 ⟶ 6 NaOH + 3 I_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_2O | 3 | -3 NaI | 5 | -5 NaIO_3 | 1 | -1 NaOH | 6 | 6 I_2 | 3 | 3 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression H_2O | 3 | -3 | ([H2O])^(-3) NaI | 5 | -5 | ([NaI])^(-5) NaIO_3 | 1 | -1 | ([NaIO3])^(-1) NaOH | 6 | 6 | ([NaOH])^6 I_2 | 3 | 3 | ([I2])^3 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 = ([H2O])^(-3) ([NaI])^(-5) ([NaIO3])^(-1) ([NaOH])^6 ([I2])^3 = (([NaOH])^6 ([I2])^3)/(([H2O])^3 ([NaI])^5 [NaIO3])

Construct the rate of reaction expression for: H_2O + NaI + NaIO_3 ⟶ NaOH + I_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: 3 H_2O + 5 NaI + NaIO_3 ⟶ 6 NaOH + 3 I_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_2O | 3 | -3 NaI | 5 | -5 NaIO_3 | 1 | -1 NaOH | 6 | 6 I_2 | 3 | 3 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_2O | 3 | -3 | -1/3 (Δ[H2O])/(Δt) NaI | 5 | -5 | -1/5 (Δ[NaI])/(Δt) NaIO_3 | 1 | -1 | -(Δ[NaIO3])/(Δt) NaOH | 6 | 6 | 1/6 (Δ[NaOH])/(Δt) I_2 | 3 | 3 | 1/3 (Δ[I2])/(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 = -1/3 (Δ[H2O])/(Δt) = -1/5 (Δ[NaI])/(Δt) = -(Δ[NaIO3])/(Δt) = 1/6 (Δ[NaOH])/(Δt) = 1/3 (Δ[I2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| water | sodium iodide | sodium iodate | sodium hydroxide | iodine formula | H_2O | NaI | NaIO_3 | NaOH | I_2 Hill formula | H_2O | INa | INaO_3 | HNaO | I_2 name | water | sodium iodide | sodium iodate | sodium hydroxide | iodine IUPAC name | water | sodium iodide | sodium iodate | sodium hydroxide | molecular iodine

| water | sodium iodide | sodium iodate | sodium hydroxide | iodine molar mass | 18.015 g/mol | 149.89424 g/mol | 197.891 g/mol | 39.997 g/mol | 253.80894 g/mol phase | liquid (at STP) | solid (at STP) | solid (at STP) | solid (at STP) | solid (at STP) melting point | 0 °C | 661 °C | 425 °C | 323 °C | 113 °C boiling point | 99.9839 °C | 1300 °C | | 1390 °C | 184 °C density | 1 g/cm^3 | 3.67 g/cm^3 | 3.56 g/cm^3 | 2.13 g/cm^3 | 4.94 g/cm^3 solubility in water | | | | soluble | surface tension | 0.0728 N/m | | | 0.07435 N/m | dynamic viscosity | 8.9×10^-4 Pa s (at 25 °C) | 0.0010446 Pa s (at 691 °C) | | 0.004 Pa s (at 350 °C) | 0.00227 Pa s (at 116 °C) odor | odorless | | | |