CuS = S + Cu

CuS cupric sulfide ⟶ S mixed sulfur + Cu copper

Balance the chemical equation algebraically: CuS ⟶ S + Cu Add stoichiometric coefficients, c_i, to the reactants and products: c_1 CuS ⟶ c_2 S + c_3 Cu Set the number of atoms in the reactants equal to the number of atoms in the products for Cu and S: Cu: | c_1 = c_3 S: | c_1 = c_2 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 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | CuS ⟶ S + Cu

⟶ +

cupric sulfide ⟶ mixed sulfur + copper

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

Construct the rate of reaction expression for: CuS ⟶ S + Cu 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: CuS ⟶ S + Cu 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 CuS | 1 | -1 S | 1 | 1 Cu | 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 CuS | 1 | -1 | -(Δ[CuS])/(Δt) S | 1 | 1 | (Δ[S])/(Δt) Cu | 1 | 1 | (Δ[Cu])/(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[CuS])/(Δt) = (Δ[S])/(Δt) = (Δ[Cu])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| cupric sulfide | mixed sulfur | copper formula | CuS | S | Cu name | cupric sulfide | mixed sulfur | copper IUPAC name | | sulfur | copper

| cupric sulfide | mixed sulfur | copper molar mass | 95.61 g/mol | 32.06 g/mol | 63.546 g/mol phase | solid (at STP) | solid (at STP) | solid (at STP) melting point | 220 °C | 112.8 °C | 1083 °C boiling point | | 444.7 °C | 2567 °C density | 4.6 g/cm^3 | 2.07 g/cm^3 | 8.96 g/cm^3 solubility in water | | | insoluble dynamic viscosity | 3.68×10^-5 Pa s (at 1250 °C) | | odor | | | odorless