HCl + Zn + H2SeO3 = H2O + ZnCl2 + Se

HCl hydrogen chloride + Zn zinc + H_2SeO_3 selenious acid ⟶ H_2O water + ZnCl_2 zinc chloride + Se gray selenium

Balance the chemical equation algebraically: HCl + Zn + H_2SeO_3 ⟶ H_2O + ZnCl_2 + Se Add stoichiometric coefficients, c_i, to the reactants and products: c_1 HCl + c_2 Zn + c_3 H_2SeO_3 ⟶ c_4 H_2O + c_5 ZnCl_2 + c_6 Se Set the number of atoms in the reactants equal to the number of atoms in the products for Cl, H, Zn, O and Se: Cl: | c_1 = 2 c_5 H: | c_1 + 2 c_3 = 2 c_4 Zn: | c_2 = c_5 O: | 3 c_3 = c_4 Se: | c_3 = c_6 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_3 = 1 and solve the system of equations for the remaining coefficients: c_1 = 4 c_2 = 2 c_3 = 1 c_4 = 3 c_5 = 2 c_6 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 4 HCl + 2 Zn + H_2SeO_3 ⟶ 3 H_2O + 2 ZnCl_2 + Se

+ + ⟶ + +

hydrogen chloride + zinc + selenious acid ⟶ water + zinc chloride + gray selenium

Construct the equilibrium constant, K, expression for: HCl + Zn + H_2SeO_3 ⟶ H_2O + ZnCl_2 + Se 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 HCl + 2 Zn + H_2SeO_3 ⟶ 3 H_2O + 2 ZnCl_2 + Se 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 HCl | 4 | -4 Zn | 2 | -2 H_2SeO_3 | 1 | -1 H_2O | 3 | 3 ZnCl_2 | 2 | 2 Se | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression HCl | 4 | -4 | ([HCl])^(-4) Zn | 2 | -2 | ([Zn])^(-2) H_2SeO_3 | 1 | -1 | ([H2SeO3])^(-1) H_2O | 3 | 3 | ([H2O])^3 ZnCl_2 | 2 | 2 | ([ZnCl2])^2 Se | 1 | 1 | [Se] 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 = ([HCl])^(-4) ([Zn])^(-2) ([H2SeO3])^(-1) ([H2O])^3 ([ZnCl2])^2 [Se] = (([H2O])^3 ([ZnCl2])^2 [Se])/(([HCl])^4 ([Zn])^2 [H2SeO3])

Construct the rate of reaction expression for: HCl + Zn + H_2SeO_3 ⟶ H_2O + ZnCl_2 + Se 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 HCl + 2 Zn + H_2SeO_3 ⟶ 3 H_2O + 2 ZnCl_2 + Se 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 HCl | 4 | -4 Zn | 2 | -2 H_2SeO_3 | 1 | -1 H_2O | 3 | 3 ZnCl_2 | 2 | 2 Se | 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 HCl | 4 | -4 | -1/4 (Δ[HCl])/(Δt) Zn | 2 | -2 | -1/2 (Δ[Zn])/(Δt) H_2SeO_3 | 1 | -1 | -(Δ[H2SeO3])/(Δt) H_2O | 3 | 3 | 1/3 (Δ[H2O])/(Δt) ZnCl_2 | 2 | 2 | 1/2 (Δ[ZnCl2])/(Δt) Se | 1 | 1 | (Δ[Se])/(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[HCl])/(Δt) = -1/2 (Δ[Zn])/(Δt) = -(Δ[H2SeO3])/(Δt) = 1/3 (Δ[H2O])/(Δt) = 1/2 (Δ[ZnCl2])/(Δt) = (Δ[Se])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| hydrogen chloride | zinc | selenious acid | water | zinc chloride | gray selenium formula | HCl | Zn | H_2SeO_3 | H_2O | ZnCl_2 | Se Hill formula | ClH | Zn | H_2O_3Se | H_2O | Cl_2Zn | Se name | hydrogen chloride | zinc | selenious acid | water | zinc chloride | gray selenium IUPAC name | hydrogen chloride | zinc | selenous acid | water | zinc dichloride | selenium