I2 + Ni = NiI2

I_2 iodine + Ni nickel ⟶ NiI_2 nickel iodide

Balance the chemical equation algebraically: I_2 + Ni ⟶ NiI_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 I_2 + c_2 Ni ⟶ c_3 NiI_2 Set the number of atoms in the reactants equal to the number of atoms in the products for I and Ni: I: | 2 c_1 = 2 c_3 Ni: | c_2 = c_3 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_1 = 1 and solve the system of equations for the remaining coefficients: c_1 = 1 c_2 = 1 c_3 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | I_2 + Ni ⟶ NiI_2

+ ⟶

iodine + nickel ⟶ nickel iodide

| iodine | nickel | nickel iodide molecular enthalpy | 0 kJ/mol | 0 kJ/mol | -78.2 kJ/mol total enthalpy | 0 kJ/mol | 0 kJ/mol | -78.2 kJ/mol | H_initial = 0 kJ/mol | | H_final = -78.2 kJ/mol ΔH_rxn^0 | -78.2 kJ/mol - 0 kJ/mol = -78.2 kJ/mol (exothermic) | |

Construct the equilibrium constant, K, expression for: I_2 + Ni ⟶ NiI_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: I_2 + Ni ⟶ NiI_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 I_2 | 1 | -1 Ni | 1 | -1 NiI_2 | 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 | 1 | -1 | ([I2])^(-1) Ni | 1 | -1 | ([Ni])^(-1) NiI_2 | 1 | 1 | [NiI2] 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])^(-1) ([Ni])^(-1) [NiI2] = ([NiI2])/([I2] [Ni])

Construct the rate of reaction expression for: I_2 + Ni ⟶ NiI_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: I_2 + Ni ⟶ NiI_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 I_2 | 1 | -1 Ni | 1 | -1 NiI_2 | 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 | 1 | -1 | -(Δ[I2])/(Δt) Ni | 1 | -1 | -(Δ[Ni])/(Δt) NiI_2 | 1 | 1 | (Δ[NiI2])/(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 = -(Δ[I2])/(Δt) = -(Δ[Ni])/(Δt) = (Δ[NiI2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| iodine | nickel | nickel iodide formula | I_2 | Ni | NiI_2 Hill formula | I_2 | Ni | I_2Ni name | iodine | nickel | nickel iodide IUPAC name | molecular iodine | nickel | diiodonickel

| iodine | nickel | nickel iodide molar mass | 253.80894 g/mol | 58.6934 g/mol | 312.5023 g/mol phase | solid (at STP) | solid (at STP) | solid (at STP) melting point | 113 °C | 1453 °C | 797 °C boiling point | 184 °C | 2732 °C | density | 4.94 g/cm^3 | 8.908 g/cm^3 | 5.83 g/cm^3 solubility in water | | insoluble | dynamic viscosity | 0.00227 Pa s (at 116 °C) | | odor | | odorless |