HI + CuCl2 = HCl + I2 + CuI

HI hydrogen iodide + CuCl_2 copper(II) chloride ⟶ HCl hydrogen chloride + I_2 iodine + CuI cuprous iodide

Balance the chemical equation algebraically: HI + CuCl_2 ⟶ HCl + I_2 + CuI Add stoichiometric coefficients, c_i, to the reactants and products: c_1 HI + c_2 CuCl_2 ⟶ c_3 HCl + c_4 I_2 + c_5 CuI Set the number of atoms in the reactants equal to the number of atoms in the products for H, I, Cl and Cu: H: | c_1 = c_3 I: | c_1 = 2 c_4 + c_5 Cl: | 2 c_2 = c_3 Cu: | c_2 = c_5 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 = 4 c_2 = 2 c_3 = 4 c_4 = 1 c_5 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 4 HI + 2 CuCl_2 ⟶ 4 HCl + I_2 + 2 CuI

+ ⟶ + +

hydrogen iodide + copper(II) chloride ⟶ hydrogen chloride + iodine + cuprous iodide

| hydrogen iodide | copper(II) chloride | hydrogen chloride | iodine | cuprous iodide molecular enthalpy | 26.5 kJ/mol | -220.1 kJ/mol | -92.3 kJ/mol | 0 kJ/mol | -67.8 kJ/mol total enthalpy | 106 kJ/mol | -440.2 kJ/mol | -369.2 kJ/mol | 0 kJ/mol | -135.6 kJ/mol | H_initial = -334.2 kJ/mol | | H_final = -504.8 kJ/mol | | ΔH_rxn^0 | -504.8 kJ/mol - -334.2 kJ/mol = -170.6 kJ/mol (exothermic) | | | |

| hydrogen iodide | copper(II) chloride | hydrogen chloride | iodine | cuprous iodide molecular free energy | 1.7 kJ/mol | -175.7 kJ/mol | -95.3 kJ/mol | 0 kJ/mol | -69.5 kJ/mol total free energy | 6.8 kJ/mol | -351.4 kJ/mol | -381.2 kJ/mol | 0 kJ/mol | -139 kJ/mol | G_initial = -344.6 kJ/mol | | G_final = -520.2 kJ/mol | | ΔG_rxn^0 | -520.2 kJ/mol - -344.6 kJ/mol = -175.6 kJ/mol (exergonic) | | | |

Construct the equilibrium constant, K, expression for: HI + CuCl_2 ⟶ HCl + I_2 + CuI 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: 4 HI + 2 CuCl_2 ⟶ 4 HCl + I_2 + 2 CuI 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 HI | 4 | -4 CuCl_2 | 2 | -2 HCl | 4 | 4 I_2 | 1 | 1 CuI | 2 | 2 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression HI | 4 | -4 | ([HI])^(-4) CuCl_2 | 2 | -2 | ([CuCl2])^(-2) HCl | 4 | 4 | ([HCl])^4 I_2 | 1 | 1 | [I2] CuI | 2 | 2 | ([CuI])^2 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 = ([HI])^(-4) ([CuCl2])^(-2) ([HCl])^4 [I2] ([CuI])^2 = (([HCl])^4 [I2] ([CuI])^2)/(([HI])^4 ([CuCl2])^2)

Construct the rate of reaction expression for: HI + CuCl_2 ⟶ HCl + I_2 + CuI 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: 4 HI + 2 CuCl_2 ⟶ 4 HCl + I_2 + 2 CuI 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 HI | 4 | -4 CuCl_2 | 2 | -2 HCl | 4 | 4 I_2 | 1 | 1 CuI | 2 | 2 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 HI | 4 | -4 | -1/4 (Δ[HI])/(Δt) CuCl_2 | 2 | -2 | -1/2 (Δ[CuCl2])/(Δt) HCl | 4 | 4 | 1/4 (Δ[HCl])/(Δt) I_2 | 1 | 1 | (Δ[I2])/(Δt) CuI | 2 | 2 | 1/2 (Δ[CuI])/(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 = -1/4 (Δ[HI])/(Δt) = -1/2 (Δ[CuCl2])/(Δt) = 1/4 (Δ[HCl])/(Δt) = (Δ[I2])/(Δt) = 1/2 (Δ[CuI])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| hydrogen iodide | copper(II) chloride | hydrogen chloride | iodine | cuprous iodide formula | HI | CuCl_2 | HCl | I_2 | CuI Hill formula | HI | Cl_2Cu | ClH | I_2 | CuI name | hydrogen iodide | copper(II) chloride | hydrogen chloride | iodine | cuprous iodide IUPAC name | hydrogen iodide | dichlorocopper | hydrogen chloride | molecular iodine | cuprous iodide

| hydrogen iodide | copper(II) chloride | hydrogen chloride | iodine | cuprous iodide molar mass | 127.912 g/mol | 134.4 g/mol | 36.46 g/mol | 253.80894 g/mol | 190.45 g/mol phase | gas (at STP) | solid (at STP) | gas (at STP) | solid (at STP) | solid (at STP) melting point | -50.76 °C | 620 °C | -114.17 °C | 113 °C | 605 °C boiling point | -35.55 °C | | -85 °C | 184 °C | 1290 °C density | 0.005228 g/cm^3 (at 25 °C) | 3.386 g/cm^3 | 0.00149 g/cm^3 (at 25 °C) | 4.94 g/cm^3 | 5.62 g/cm^3 solubility in water | very soluble | | miscible | | insoluble dynamic viscosity | 0.001321 Pa s (at -39 °C) | | | 0.00227 Pa s (at 116 °C) |