Input interpretation
H_2O_2 hydrogen peroxide + As_2S_3 arsenic(III) sulfide ⟶ H_2O water + H_2SO_4 sulfuric acid + H_3AsO_4 arsenic acid, solid
Balanced equation
Balance the chemical equation algebraically: H_2O_2 + As_2S_3 ⟶ H_2O + H_2SO_4 + H_3AsO_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2O_2 + c_2 As_2S_3 ⟶ c_3 H_2O + c_4 H_2SO_4 + c_5 H_3AsO_4 Set the number of atoms in the reactants equal to the number of atoms in the products for H, O, As and S: H: | 2 c_1 = 2 c_3 + 2 c_4 + 3 c_5 O: | 2 c_1 = c_3 + 4 c_4 + 4 c_5 As: | 2 c_2 = c_5 S: | 3 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_2 = 1 and solve the system of equations for the remaining coefficients: c_1 = 14 c_2 = 1 c_3 = 8 c_4 = 3 c_5 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 14 H_2O_2 + As_2S_3 ⟶ 8 H_2O + 3 H_2SO_4 + 2 H_3AsO_4
Structures
+ ⟶ + +
Names
hydrogen peroxide + arsenic(III) sulfide ⟶ water + sulfuric acid + arsenic acid, solid
Equilibrium constant
Construct the equilibrium constant, K, expression for: H_2O_2 + As_2S_3 ⟶ H_2O + H_2SO_4 + H_3AsO_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: 14 H_2O_2 + As_2S_3 ⟶ 8 H_2O + 3 H_2SO_4 + 2 H_3AsO_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 H_2O_2 | 14 | -14 As_2S_3 | 1 | -1 H_2O | 8 | 8 H_2SO_4 | 3 | 3 H_3AsO_4 | 2 | 2 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression H_2O_2 | 14 | -14 | ([H2O2])^(-14) As_2S_3 | 1 | -1 | ([As2S3])^(-1) H_2O | 8 | 8 | ([H2O])^8 H_2SO_4 | 3 | 3 | ([H2SO4])^3 H_3AsO_4 | 2 | 2 | ([H3AsO4])^2 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 = ([H2O2])^(-14) ([As2S3])^(-1) ([H2O])^8 ([H2SO4])^3 ([H3AsO4])^2 = (([H2O])^8 ([H2SO4])^3 ([H3AsO4])^2)/(([H2O2])^14 [As2S3])
Rate of reaction
Construct the rate of reaction expression for: H_2O_2 + As_2S_3 ⟶ H_2O + H_2SO_4 + H_3AsO_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: 14 H_2O_2 + As_2S_3 ⟶ 8 H_2O + 3 H_2SO_4 + 2 H_3AsO_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 H_2O_2 | 14 | -14 As_2S_3 | 1 | -1 H_2O | 8 | 8 H_2SO_4 | 3 | 3 H_3AsO_4 | 2 | 2 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_2O_2 | 14 | -14 | -1/14 (Δ[H2O2])/(Δt) As_2S_3 | 1 | -1 | -(Δ[As2S3])/(Δt) H_2O | 8 | 8 | 1/8 (Δ[H2O])/(Δt) H_2SO_4 | 3 | 3 | 1/3 (Δ[H2SO4])/(Δt) H_3AsO_4 | 2 | 2 | 1/2 (Δ[H3AsO4])/(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 = -1/14 (Δ[H2O2])/(Δt) = -(Δ[As2S3])/(Δt) = 1/8 (Δ[H2O])/(Δt) = 1/3 (Δ[H2SO4])/(Δt) = 1/2 (Δ[H3AsO4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)
Chemical names and formulas
| hydrogen peroxide | arsenic(III) sulfide | water | sulfuric acid | arsenic acid, solid formula | H_2O_2 | As_2S_3 | H_2O | H_2SO_4 | H_3AsO_4 Hill formula | H_2O_2 | As_2S_3 | H_2O | H_2O_4S | AsH_3O_4 name | hydrogen peroxide | arsenic(III) sulfide | water | sulfuric acid | arsenic acid, solid IUPAC name | hydrogen peroxide | | water | sulfuric acid | arsoric acid
Substance properties
| hydrogen peroxide | arsenic(III) sulfide | water | sulfuric acid | arsenic acid, solid molar mass | 34.014 g/mol | 246 g/mol | 18.015 g/mol | 98.07 g/mol | 141.94 g/mol phase | liquid (at STP) | solid (at STP) | liquid (at STP) | liquid (at STP) | solid (at STP) melting point | -0.43 °C | 300 °C | 0 °C | 10.371 °C | 35.5 °C boiling point | 150.2 °C | | 99.9839 °C | 279.6 °C | 160 °C density | 1.44 g/cm^3 | 3.43 g/cm^3 | 1 g/cm^3 | 1.8305 g/cm^3 | 2.2 g/cm^3 solubility in water | miscible | | | very soluble | surface tension | 0.0804 N/m | | 0.0728 N/m | 0.0735 N/m | dynamic viscosity | 0.001249 Pa s (at 20 °C) | | 8.9×10^-4 Pa s (at 25 °C) | 0.021 Pa s (at 25 °C) | odor | | | odorless | odorless |
Units