Cl2 + Si = SiCl

Cl_2 chlorine + Si silicon ⟶ SiCl

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

+ ⟶ SiCl

chlorine + silicon ⟶ SiCl

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

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

| chlorine | silicon | SiCl formula | Cl_2 | Si | SiCl Hill formula | Cl_2 | Si | ClSi name | chlorine | silicon | IUPAC name | molecular chlorine | silicon |

| chlorine | silicon | SiCl molar mass | 70.9 g/mol | 28.085 g/mol | 63.53 g/mol phase | gas (at STP) | solid (at STP) | melting point | -101 °C | 1410 °C | boiling point | -34 °C | 2355 °C | density | 0.003214 g/cm^3 (at 0 °C) | 2.33 g/cm^3 | solubility in water | | insoluble |