I2 + NH3 = H2 + N2I6

I_2 iodine + NH_3 ammonia ⟶ H_2 hydrogen + N2I6

Balance the chemical equation algebraically: I_2 + NH_3 ⟶ H_2 + N2I6 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 I_2 + c_2 NH_3 ⟶ c_3 H_2 + c_4 N2I6 Set the number of atoms in the reactants equal to the number of atoms in the products for I, H and N: I: | 2 c_1 = 6 c_4 H: | 3 c_2 = 2 c_3 N: | 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_4 = 1 and solve the system of equations for the remaining coefficients: c_1 = 3 c_2 = 2 c_3 = 3 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 3 I_2 + 2 NH_3 ⟶ 3 H_2 + N2I6

+ ⟶ + N2I6

iodine + ammonia ⟶ hydrogen + N2I6

Construct the equilibrium constant, K, expression for: I_2 + NH_3 ⟶ H_2 + N2I6 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 I_2 + 2 NH_3 ⟶ 3 H_2 + N2I6 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 I_2 | 3 | -3 NH_3 | 2 | -2 H_2 | 3 | 3 N2I6 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression I_2 | 3 | -3 | ([I2])^(-3) NH_3 | 2 | -2 | ([NH3])^(-2) H_2 | 3 | 3 | ([H2])^3 N2I6 | 1 | 1 | [N2I6] 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 = ([I2])^(-3) ([NH3])^(-2) ([H2])^3 [N2I6] = (([H2])^3 [N2I6])/(([I2])^3 ([NH3])^2)

Construct the rate of reaction expression for: I_2 + NH_3 ⟶ H_2 + N2I6 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 I_2 + 2 NH_3 ⟶ 3 H_2 + N2I6 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 I_2 | 3 | -3 NH_3 | 2 | -2 H_2 | 3 | 3 N2I6 | 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 I_2 | 3 | -3 | -1/3 (Δ[I2])/(Δt) NH_3 | 2 | -2 | -1/2 (Δ[NH3])/(Δt) H_2 | 3 | 3 | 1/3 (Δ[H2])/(Δt) N2I6 | 1 | 1 | (Δ[N2I6])/(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[I2])/(Δt) = -1/2 (Δ[NH3])/(Δt) = 1/3 (Δ[H2])/(Δt) = (Δ[N2I6])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| iodine | ammonia | hydrogen | N2I6 formula | I_2 | NH_3 | H_2 | N2I6 Hill formula | I_2 | H_3N | H_2 | I6N2 name | iodine | ammonia | hydrogen | IUPAC name | molecular iodine | ammonia | molecular hydrogen |

| iodine | ammonia | hydrogen | N2I6 molar mass | 253.80894 g/mol | 17.031 g/mol | 2.016 g/mol | 789.441 g/mol phase | solid (at STP) | gas (at STP) | gas (at STP) | melting point | 113 °C | -77.73 °C | -259.2 °C | boiling point | 184 °C | -33.33 °C | -252.8 °C | density | 4.94 g/cm^3 | 6.96×10^-4 g/cm^3 (at 25 °C) | 8.99×10^-5 g/cm^3 (at 0 °C) | surface tension | | 0.0234 N/m | | dynamic viscosity | 0.00227 Pa s (at 116 °C) | 1.009×10^-5 Pa s (at 25 °C) | 8.9×10^-6 Pa s (at 25 °C) | odor | | | odorless |