HI + RaCl2 = HCl + RaI2

HI hydrogen iodide + RaCl2 ⟶ HCl hydrogen chloride + RaI2

Balance the chemical equation algebraically: HI + RaCl2 ⟶ HCl + RaI2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 HI + c_2 RaCl2 ⟶ c_3 HCl + c_4 RaI2 Set the number of atoms in the reactants equal to the number of atoms in the products for H, I, Ra and Cl: H: | c_1 = c_3 I: | c_1 = 2 c_4 Ra: | c_2 = c_4 Cl: | 2 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_2 = 1 and solve the system of equations for the remaining coefficients: c_1 = 2 c_2 = 1 c_3 = 2 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 HI + RaCl2 ⟶ 2 HCl + RaI2

+ RaCl2 ⟶ + RaI2

hydrogen iodide + RaCl2 ⟶ hydrogen chloride + RaI2

Construct the equilibrium constant, K, expression for: HI + RaCl2 ⟶ HCl + RaI2 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: 2 HI + RaCl2 ⟶ 2 HCl + RaI2 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 | 2 | -2 RaCl2 | 1 | -1 HCl | 2 | 2 RaI2 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression HI | 2 | -2 | ([HI])^(-2) RaCl2 | 1 | -1 | ([RaCl2])^(-1) HCl | 2 | 2 | ([HCl])^2 RaI2 | 1 | 1 | [RaI2] 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])^(-2) ([RaCl2])^(-1) ([HCl])^2 [RaI2] = (([HCl])^2 [RaI2])/(([HI])^2 [RaCl2])

Construct the rate of reaction expression for: HI + RaCl2 ⟶ HCl + RaI2 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: 2 HI + RaCl2 ⟶ 2 HCl + RaI2 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 | 2 | -2 RaCl2 | 1 | -1 HCl | 2 | 2 RaI2 | 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 HI | 2 | -2 | -1/2 (Δ[HI])/(Δt) RaCl2 | 1 | -1 | -(Δ[RaCl2])/(Δt) HCl | 2 | 2 | 1/2 (Δ[HCl])/(Δt) RaI2 | 1 | 1 | (Δ[RaI2])/(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 = -1/2 (Δ[HI])/(Δt) = -(Δ[RaCl2])/(Δt) = 1/2 (Δ[HCl])/(Δt) = (Δ[RaI2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| hydrogen iodide | RaCl2 | hydrogen chloride | RaI2 formula | HI | RaCl2 | HCl | RaI2 Hill formula | HI | Cl2Ra | ClH | I2Ra name | hydrogen iodide | | hydrogen chloride |

| hydrogen iodide | RaCl2 | hydrogen chloride | RaI2 molar mass | 127.912 g/mol | 297 g/mol | 36.46 g/mol | 480 g/mol phase | gas (at STP) | | gas (at STP) | melting point | -50.76 °C | | -114.17 °C | boiling point | -35.55 °C | | -85 °C | density | 0.005228 g/cm^3 (at 25 °C) | | 0.00149 g/cm^3 (at 25 °C) | solubility in water | very soluble | | miscible | dynamic viscosity | 0.001321 Pa s (at -39 °C) | | |