H2 + CrCl3 = HCl + CrCl

H_2 hydrogen + CrCl_3 chromic chloride ⟶ HCl hydrogen chloride + CrCl

Balance the chemical equation algebraically: H_2 + CrCl_3 ⟶ HCl + CrCl Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2 + c_2 CrCl_3 ⟶ c_3 HCl + c_4 CrCl Set the number of atoms in the reactants equal to the number of atoms in the products for H, Cl and Cr: H: | 2 c_1 = c_3 Cl: | 3 c_2 = c_3 + c_4 Cr: | c_2 = c_4 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 = 2 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | H_2 + CrCl_3 ⟶ 2 HCl + CrCl

+ ⟶ + CrCl

hydrogen + chromic chloride ⟶ hydrogen chloride + CrCl

Construct the equilibrium constant, K, expression for: H_2 + CrCl_3 ⟶ HCl + CrCl 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: H_2 + CrCl_3 ⟶ 2 HCl + CrCl 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 H_2 | 1 | -1 CrCl_3 | 1 | -1 HCl | 2 | 2 CrCl | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression H_2 | 1 | -1 | ([H2])^(-1) CrCl_3 | 1 | -1 | ([CrCl3])^(-1) HCl | 2 | 2 | ([HCl])^2 CrCl | 1 | 1 | [CrCl] 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 = ([H2])^(-1) ([CrCl3])^(-1) ([HCl])^2 [CrCl] = (([HCl])^2 [CrCl])/([H2] [CrCl3])

Construct the rate of reaction expression for: H_2 + CrCl_3 ⟶ HCl + CrCl 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: H_2 + CrCl_3 ⟶ 2 HCl + CrCl 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 H_2 | 1 | -1 CrCl_3 | 1 | -1 HCl | 2 | 2 CrCl | 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 H_2 | 1 | -1 | -(Δ[H2])/(Δt) CrCl_3 | 1 | -1 | -(Δ[CrCl3])/(Δt) HCl | 2 | 2 | 1/2 (Δ[HCl])/(Δt) CrCl | 1 | 1 | (Δ[CrCl])/(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[H2])/(Δt) = -(Δ[CrCl3])/(Δt) = 1/2 (Δ[HCl])/(Δt) = (Δ[CrCl])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| hydrogen | chromic chloride | hydrogen chloride | CrCl formula | H_2 | CrCl_3 | HCl | CrCl Hill formula | H_2 | Cl_3Cr | ClH | ClCr name | hydrogen | chromic chloride | hydrogen chloride | IUPAC name | molecular hydrogen | trichlorochromium | hydrogen chloride |

| hydrogen | chromic chloride | hydrogen chloride | CrCl molar mass | 2.016 g/mol | 158.3 g/mol | 36.46 g/mol | 87.45 g/mol phase | gas (at STP) | solid (at STP) | gas (at STP) | melting point | -259.2 °C | 1152 °C | -114.17 °C | boiling point | -252.8 °C | | -85 °C | density | 8.99×10^-5 g/cm^3 (at 0 °C) | 2.87 g/cm^3 | 0.00149 g/cm^3 (at 25 °C) | solubility in water | | slightly soluble | miscible | dynamic viscosity | 8.9×10^-6 Pa s (at 25 °C) | | | odor | odorless | | |