BCl3 = Cl2 + B2Cl4

BCl_3 boron trichloride ⟶ Cl_2 chlorine + B_2Cl_4 tetrachloradiborane

Balance the chemical equation algebraically: BCl_3 ⟶ Cl_2 + B_2Cl_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 BCl_3 ⟶ c_2 Cl_2 + c_3 B_2Cl_4 Set the number of atoms in the reactants equal to the number of atoms in the products for B and Cl: B: | c_1 = 2 c_3 Cl: | 3 c_1 = 2 c_2 + 4 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 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 BCl_3 ⟶ Cl_2 + B_2Cl_4

⟶ +

boron trichloride ⟶ chlorine + tetrachloradiborane

Construct the equilibrium constant, K, expression for: BCl_3 ⟶ Cl_2 + B_2Cl_4 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 BCl_3 ⟶ Cl_2 + B_2Cl_4 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 BCl_3 | 2 | -2 Cl_2 | 1 | 1 B_2Cl_4 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression BCl_3 | 2 | -2 | ([BCl3])^(-2) Cl_2 | 1 | 1 | [Cl2] B_2Cl_4 | 1 | 1 | [B2Cl4] 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 = ([BCl3])^(-2) [Cl2] [B2Cl4] = ([Cl2] [B2Cl4])/([BCl3])^2

Construct the rate of reaction expression for: BCl_3 ⟶ Cl_2 + B_2Cl_4 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 BCl_3 ⟶ Cl_2 + B_2Cl_4 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 BCl_3 | 2 | -2 Cl_2 | 1 | 1 B_2Cl_4 | 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 BCl_3 | 2 | -2 | -1/2 (Δ[BCl3])/(Δt) Cl_2 | 1 | 1 | (Δ[Cl2])/(Δt) B_2Cl_4 | 1 | 1 | (Δ[B2Cl4])/(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[BCl3])/(Δt) = (Δ[Cl2])/(Δt) = (Δ[B2Cl4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| boron trichloride | chlorine | tetrachloradiborane formula | BCl_3 | Cl_2 | B_2Cl_4 name | boron trichloride | chlorine | tetrachloradiborane IUPAC name | trichloroborane | molecular chlorine | dichloro(dichloroboranyl)borane

| boron trichloride | chlorine | tetrachloradiborane molar mass | 117.2 g/mol | 70.9 g/mol | 163.4 g/mol phase | gas (at STP) | gas (at STP) | melting point | -107 °C | -101 °C | boiling point | 12.4 °C | -34 °C | density | 0.004789 g/cm^3 (at 25 °C) | 0.003214 g/cm^3 (at 0 °C) | solubility in water | decomposes | | surface tension | 0.0167 N/m | | dynamic viscosity | 0.00104 Pa s (at 10 °C) | |