H2S + H2O2 = H2O + S8

H_2S hydrogen sulfide + H_2O_2 hydrogen peroxide ⟶ H_2O water + S_8 rhombic sulfur

Balance the chemical equation algebraically: H_2S + H_2O_2 ⟶ H_2O + S_8 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2S + c_2 H_2O_2 ⟶ c_3 H_2O + c_4 S_8 Set the number of atoms in the reactants equal to the number of atoms in the products for H, S and O: H: | 2 c_1 + 2 c_2 = 2 c_3 S: | c_1 = 8 c_4 O: | 2 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_4 = 1 and solve the system of equations for the remaining coefficients: c_1 = 8 c_2 = 8 c_3 = 16 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 8 H_2S + 8 H_2O_2 ⟶ 16 H_2O + S_8

+ ⟶ +

hydrogen sulfide + hydrogen peroxide ⟶ water + rhombic sulfur

Construct the equilibrium constant, K, expression for: H_2S + H_2O_2 ⟶ H_2O + S_8 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: 8 H_2S + 8 H_2O_2 ⟶ 16 H_2O + S_8 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_2S | 8 | -8 H_2O_2 | 8 | -8 H_2O | 16 | 16 S_8 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression H_2S | 8 | -8 | ([H2S])^(-8) H_2O_2 | 8 | -8 | ([H2O2])^(-8) H_2O | 16 | 16 | ([H2O])^16 S_8 | 1 | 1 | [S8] 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 = ([H2S])^(-8) ([H2O2])^(-8) ([H2O])^16 [S8] = (([H2O])^16 [S8])/(([H2S])^8 ([H2O2])^8)

Construct the rate of reaction expression for: H_2S + H_2O_2 ⟶ H_2O + S_8 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: 8 H_2S + 8 H_2O_2 ⟶ 16 H_2O + S_8 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_2S | 8 | -8 H_2O_2 | 8 | -8 H_2O | 16 | 16 S_8 | 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_2S | 8 | -8 | -1/8 (Δ[H2S])/(Δt) H_2O_2 | 8 | -8 | -1/8 (Δ[H2O2])/(Δt) H_2O | 16 | 16 | 1/16 (Δ[H2O])/(Δt) S_8 | 1 | 1 | (Δ[S8])/(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 = -1/8 (Δ[H2S])/(Δt) = -1/8 (Δ[H2O2])/(Δt) = 1/16 (Δ[H2O])/(Δt) = (Δ[S8])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| hydrogen sulfide | hydrogen peroxide | water | rhombic sulfur formula | H_2S | H_2O_2 | H_2O | S_8 name | hydrogen sulfide | hydrogen peroxide | water | rhombic sulfur IUPAC name | hydrogen sulfide | hydrogen peroxide | water | octathiocane

| hydrogen sulfide | hydrogen peroxide | water | rhombic sulfur molar mass | 34.08 g/mol | 34.014 g/mol | 18.015 g/mol | 256.5 g/mol phase | gas (at STP) | liquid (at STP) | liquid (at STP) | solid (at STP) melting point | -85 °C | -0.43 °C | 0 °C | boiling point | -60 °C | 150.2 °C | 99.9839 °C | density | 0.001393 g/cm^3 (at 25 °C) | 1.44 g/cm^3 | 1 g/cm^3 | 2.07 g/cm^3 solubility in water | | miscible | | surface tension | | 0.0804 N/m | 0.0728 N/m | dynamic viscosity | 1.239×10^-5 Pa s (at 25 °C) | 0.001249 Pa s (at 20 °C) | 8.9×10^-4 Pa s (at 25 °C) | odor | | | odorless |