Input interpretation
HNO_3 nitric acid + FeS ferrous sulfide ⟶ H_2O water + NO_2 nitrogen dioxide + Fe_2(SO_4)_3·xH_2O iron(III) sulfate hydrate + Fe(NO_3)_3 ferric nitrate
Balanced equation
Balance the chemical equation algebraically: HNO_3 + FeS ⟶ H_2O + NO_2 + Fe_2(SO_4)_3·xH_2O + Fe(NO_3)_3 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 HNO_3 + c_2 FeS ⟶ c_3 H_2O + c_4 NO_2 + c_5 Fe_2(SO_4)_3·xH_2O + c_6 Fe(NO_3)_3 Set the number of atoms in the reactants equal to the number of atoms in the products for H, N, O, Fe and S: H: | c_1 = 2 c_3 N: | c_1 = c_4 + 3 c_6 O: | 3 c_1 = c_3 + 2 c_4 + 12 c_5 + 9 c_6 Fe: | c_2 = 2 c_5 + c_6 S: | c_2 = 3 c_5 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_5 = 1 and solve the system of equations for the remaining coefficients: c_1 = 30 c_2 = 3 c_3 = 15 c_4 = 27 c_5 = 1 c_6 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 30 HNO_3 + 3 FeS ⟶ 15 H_2O + 27 NO_2 + Fe_2(SO_4)_3·xH_2O + Fe(NO_3)_3
Structures
+ ⟶ + + +
Names
nitric acid + ferrous sulfide ⟶ water + nitrogen dioxide + iron(III) sulfate hydrate + ferric nitrate
Equilibrium constant
Construct the equilibrium constant, K, expression for: HNO_3 + FeS ⟶ H_2O + NO_2 + Fe_2(SO_4)_3·xH_2O + Fe(NO_3)_3 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: 30 HNO_3 + 3 FeS ⟶ 15 H_2O + 27 NO_2 + Fe_2(SO_4)_3·xH_2O + Fe(NO_3)_3 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 HNO_3 | 30 | -30 FeS | 3 | -3 H_2O | 15 | 15 NO_2 | 27 | 27 Fe_2(SO_4)_3·xH_2O | 1 | 1 Fe(NO_3)_3 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression HNO_3 | 30 | -30 | ([HNO3])^(-30) FeS | 3 | -3 | ([FeS])^(-3) H_2O | 15 | 15 | ([H2O])^15 NO_2 | 27 | 27 | ([NO2])^27 Fe_2(SO_4)_3·xH_2O | 1 | 1 | [Fe2(SO4)3·xH2O] Fe(NO_3)_3 | 1 | 1 | [Fe(NO3)3] 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 = ([HNO3])^(-30) ([FeS])^(-3) ([H2O])^15 ([NO2])^27 [Fe2(SO4)3·xH2O] [Fe(NO3)3] = (([H2O])^15 ([NO2])^27 [Fe2(SO4)3·xH2O] [Fe(NO3)3])/(([HNO3])^30 ([FeS])^3)
Rate of reaction
Construct the rate of reaction expression for: HNO_3 + FeS ⟶ H_2O + NO_2 + Fe_2(SO_4)_3·xH_2O + Fe(NO_3)_3 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: 30 HNO_3 + 3 FeS ⟶ 15 H_2O + 27 NO_2 + Fe_2(SO_4)_3·xH_2O + Fe(NO_3)_3 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 HNO_3 | 30 | -30 FeS | 3 | -3 H_2O | 15 | 15 NO_2 | 27 | 27 Fe_2(SO_4)_3·xH_2O | 1 | 1 Fe(NO_3)_3 | 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 HNO_3 | 30 | -30 | -1/30 (Δ[HNO3])/(Δt) FeS | 3 | -3 | -1/3 (Δ[FeS])/(Δt) H_2O | 15 | 15 | 1/15 (Δ[H2O])/(Δt) NO_2 | 27 | 27 | 1/27 (Δ[NO2])/(Δt) Fe_2(SO_4)_3·xH_2O | 1 | 1 | (Δ[Fe2(SO4)3·xH2O])/(Δt) Fe(NO_3)_3 | 1 | 1 | (Δ[Fe(NO3)3])/(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 = -1/30 (Δ[HNO3])/(Δt) = -1/3 (Δ[FeS])/(Δt) = 1/15 (Δ[H2O])/(Δt) = 1/27 (Δ[NO2])/(Δt) = (Δ[Fe2(SO4)3·xH2O])/(Δt) = (Δ[Fe(NO3)3])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)
Chemical names and formulas
| nitric acid | ferrous sulfide | water | nitrogen dioxide | iron(III) sulfate hydrate | ferric nitrate formula | HNO_3 | FeS | H_2O | NO_2 | Fe_2(SO_4)_3·xH_2O | Fe(NO_3)_3 Hill formula | HNO_3 | FeS | H_2O | NO_2 | Fe_2O_12S_3 | FeN_3O_9 name | nitric acid | ferrous sulfide | water | nitrogen dioxide | iron(III) sulfate hydrate | ferric nitrate IUPAC name | nitric acid | | water | Nitrogen dioxide | diferric trisulfate | iron(+3) cation trinitrate