H2SO3 + H2SeO4 = H2SO4 + H2Se

H_2SO_3 sulfurous acid + H_2SeO_4 selenic acid ⟶ H_2SO_4 sulfuric acid + SeH_2 hydrogen selenide

Balance the chemical equation algebraically: H_2SO_3 + H_2SeO_4 ⟶ H_2SO_4 + SeH_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2SO_3 + c_2 H_2SeO_4 ⟶ c_3 H_2SO_4 + c_4 SeH_2 Set the number of atoms in the reactants equal to the number of atoms in the products for H, O, S and Se: H: | 2 c_1 + 2 c_2 = 2 c_3 + 2 c_4 O: | 3 c_1 + 4 c_2 = 4 c_3 S: | c_1 = c_3 Se: | 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 = 4 c_2 = 1 c_3 = 4 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 4 H_2SO_3 + H_2SeO_4 ⟶ 4 H_2SO_4 + SeH_2

+ ⟶ +

sulfurous acid + selenic acid ⟶ sulfuric acid + hydrogen selenide

Construct the equilibrium constant, K, expression for: H_2SO_3 + H_2SeO_4 ⟶ H_2SO_4 + SeH_2 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: 4 H_2SO_3 + H_2SeO_4 ⟶ 4 H_2SO_4 + SeH_2 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_2SO_3 | 4 | -4 H_2SeO_4 | 1 | -1 H_2SO_4 | 4 | 4 SeH_2 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression H_2SO_3 | 4 | -4 | ([H2SO3])^(-4) H_2SeO_4 | 1 | -1 | ([H2SeO4])^(-1) H_2SO_4 | 4 | 4 | ([H2SO4])^4 SeH_2 | 1 | 1 | [SeH2] 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 = ([H2SO3])^(-4) ([H2SeO4])^(-1) ([H2SO4])^4 [SeH2] = (([H2SO4])^4 [SeH2])/(([H2SO3])^4 [H2SeO4])

Construct the rate of reaction expression for: H_2SO_3 + H_2SeO_4 ⟶ H_2SO_4 + SeH_2 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: 4 H_2SO_3 + H_2SeO_4 ⟶ 4 H_2SO_4 + SeH_2 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_2SO_3 | 4 | -4 H_2SeO_4 | 1 | -1 H_2SO_4 | 4 | 4 SeH_2 | 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_2SO_3 | 4 | -4 | -1/4 (Δ[H2SO3])/(Δt) H_2SeO_4 | 1 | -1 | -(Δ[H2SeO4])/(Δt) H_2SO_4 | 4 | 4 | 1/4 (Δ[H2SO4])/(Δt) SeH_2 | 1 | 1 | (Δ[SeH2])/(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 = -1/4 (Δ[H2SO3])/(Δt) = -(Δ[H2SeO4])/(Δt) = 1/4 (Δ[H2SO4])/(Δt) = (Δ[SeH2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| sulfurous acid | selenic acid | sulfuric acid | hydrogen selenide formula | H_2SO_3 | H_2SeO_4 | H_2SO_4 | SeH_2 Hill formula | H_2O_3S | H_2O_4Se | H_2O_4S | H_2Se name | sulfurous acid | selenic acid | sulfuric acid | hydrogen selenide

| sulfurous acid | selenic acid | sulfuric acid | hydrogen selenide molar mass | 82.07 g/mol | 144.98 g/mol | 98.07 g/mol | 80.987 g/mol phase | | | liquid (at STP) | melting point | | | 10.371 °C | boiling point | | | 279.6 °C | density | 1.03 g/cm^3 | 2.511 g/cm^3 | 1.8305 g/cm^3 | solubility in water | very soluble | | very soluble | surface tension | | | 0.0735 N/m | dynamic viscosity | | | 0.021 Pa s (at 25 °C) | odor | | | odorless |