C + As2O3 = CO2 + As4

C activated charcoal + As_2O_3 arsenic trioxide ⟶ CO_2 carbon dioxide + As_4 yellow arsenic

Balance the chemical equation algebraically: C + As_2O_3 ⟶ CO_2 + As_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 C + c_2 As_2O_3 ⟶ c_3 CO_2 + c_4 As_4 Set the number of atoms in the reactants equal to the number of atoms in the products for C, As and O: C: | c_1 = c_3 As: | 2 c_2 = 4 c_4 O: | 3 c_2 = 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_4 = 1 and solve the system of equations for the remaining coefficients: c_1 = 3 c_2 = 2 c_3 = 3 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 3 C + 2 As_2O_3 ⟶ 3 CO_2 + As_4

+ ⟶ +

activated charcoal + arsenic trioxide ⟶ carbon dioxide + yellow arsenic

Construct the equilibrium constant, K, expression for: C + As_2O_3 ⟶ CO_2 + As_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: 3 C + 2 As_2O_3 ⟶ 3 CO_2 + As_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 C | 3 | -3 As_2O_3 | 2 | -2 CO_2 | 3 | 3 As_4 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression C | 3 | -3 | ([C])^(-3) As_2O_3 | 2 | -2 | ([As2O3])^(-2) CO_2 | 3 | 3 | ([CO2])^3 As_4 | 1 | 1 | [As4] 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 = ([C])^(-3) ([As2O3])^(-2) ([CO2])^3 [As4] = (([CO2])^3 [As4])/(([C])^3 ([As2O3])^2)

Construct the rate of reaction expression for: C + As_2O_3 ⟶ CO_2 + As_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: 3 C + 2 As_2O_3 ⟶ 3 CO_2 + As_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 C | 3 | -3 As_2O_3 | 2 | -2 CO_2 | 3 | 3 As_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 C | 3 | -3 | -1/3 (Δ[C])/(Δt) As_2O_3 | 2 | -2 | -1/2 (Δ[As2O3])/(Δt) CO_2 | 3 | 3 | 1/3 (Δ[CO2])/(Δt) As_4 | 1 | 1 | (Δ[As4])/(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 = -1/3 (Δ[C])/(Δt) = -1/2 (Δ[As2O3])/(Δt) = 1/3 (Δ[CO2])/(Δt) = (Δ[As4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| activated charcoal | arsenic trioxide | carbon dioxide | yellow arsenic formula | C | As_2O_3 | CO_2 | As_4 name | activated charcoal | arsenic trioxide | carbon dioxide | yellow arsenic IUPAC name | carbon | 2, 4, 5-trioxa-1, 3-diarsabicyclo[1.1.1]pentane | carbon dioxide |

| activated charcoal | arsenic trioxide | carbon dioxide | yellow arsenic molar mass | 12.011 g/mol | 197.84 g/mol | 44.009 g/mol | 299.68638 g/mol phase | solid (at STP) | solid (at STP) | gas (at STP) | solid (at STP) melting point | 3550 °C | 312 °C | -56.56 °C (at triple point) | boiling point | 4027 °C | 465 °C | -78.5 °C (at sublimation point) | density | 2.26 g/cm^3 | 4.15 g/cm^3 | 0.00184212 g/cm^3 (at 20 °C) | 1.97 g/cm^3 solubility in water | insoluble | | | dynamic viscosity | | | 1.491×10^-5 Pa s (at 25 °C) | odor | | | odorless |