C + Cr2O3 = CO2 + Cr

C activated charcoal + Cr_2O_3 chromium(III) oxide ⟶ CO_2 carbon dioxide + Cr chromium

Balance the chemical equation algebraically: C + Cr_2O_3 ⟶ CO_2 + Cr Add stoichiometric coefficients, c_i, to the reactants and products: c_1 C + c_2 Cr_2O_3 ⟶ c_3 CO_2 + c_4 Cr Set the number of atoms in the reactants equal to the number of atoms in the products for C, Cr and O: C: | c_1 = c_3 Cr: | 2 c_2 = 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_2 = 1 and solve the system of equations for the remaining coefficients: c_1 = 3/2 c_2 = 1 c_3 = 3/2 c_4 = 2 Multiply by the least common denominator, 2, to eliminate fractional coefficients: c_1 = 3 c_2 = 2 c_3 = 3 c_4 = 4 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 3 C + 2 Cr_2O_3 ⟶ 3 CO_2 + 4 Cr

+ ⟶ +

activated charcoal + chromium(III) oxide ⟶ carbon dioxide + chromium

Construct the equilibrium constant, K, expression for: C + Cr_2O_3 ⟶ CO_2 + Cr 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 Cr_2O_3 ⟶ 3 CO_2 + 4 Cr 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 Cr_2O_3 | 2 | -2 CO_2 | 3 | 3 Cr | 4 | 4 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) Cr_2O_3 | 2 | -2 | ([Cr2O3])^(-2) CO_2 | 3 | 3 | ([CO2])^3 Cr | 4 | 4 | ([Cr])^4 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) ([Cr2O3])^(-2) ([CO2])^3 ([Cr])^4 = (([CO2])^3 ([Cr])^4)/(([C])^3 ([Cr2O3])^2)

Construct the rate of reaction expression for: C + Cr_2O_3 ⟶ CO_2 + Cr 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 Cr_2O_3 ⟶ 3 CO_2 + 4 Cr 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 Cr_2O_3 | 2 | -2 CO_2 | 3 | 3 Cr | 4 | 4 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) Cr_2O_3 | 2 | -2 | -1/2 (Δ[Cr2O3])/(Δt) CO_2 | 3 | 3 | 1/3 (Δ[CO2])/(Δt) Cr | 4 | 4 | 1/4 (Δ[Cr])/(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[Cr2O3])/(Δt) = 1/3 (Δ[CO2])/(Δt) = 1/4 (Δ[Cr])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| activated charcoal | chromium(III) oxide | carbon dioxide | chromium formula | C | Cr_2O_3 | CO_2 | Cr name | activated charcoal | chromium(III) oxide | carbon dioxide | chromium IUPAC name | carbon | | carbon dioxide | chromium

| activated charcoal | chromium(III) oxide | carbon dioxide | chromium molar mass | 12.011 g/mol | 151.99 g/mol | 44.009 g/mol | 51.9961 g/mol phase | solid (at STP) | solid (at STP) | gas (at STP) | solid (at STP) melting point | 3550 °C | 2435 °C | -56.56 °C (at triple point) | 1857 °C boiling point | 4027 °C | 4000 °C | -78.5 °C (at sublimation point) | 2672 °C density | 2.26 g/cm^3 | 4.8 g/cm^3 | 0.00184212 g/cm^3 (at 20 °C) | 7.14 g/cm^3 solubility in water | insoluble | insoluble | | insoluble dynamic viscosity | | | 1.491×10^-5 Pa s (at 25 °C) | odor | | | odorless | odorless