HNO3 + Sb = H2O + NO2 + Sb2O5

HNO_3 nitric acid + Sb gray antimony ⟶ H_2O water + NO_2 nitrogen dioxide + Sb_2O_5 antimony pentoxide

Balance the chemical equation algebraically: HNO_3 + Sb ⟶ H_2O + NO_2 + Sb_2O_5 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 HNO_3 + c_2 Sb ⟶ c_3 H_2O + c_4 NO_2 + c_5 Sb_2O_5 Set the number of atoms in the reactants equal to the number of atoms in the products for H, N, O and Sb: H: | c_1 = 2 c_3 N: | c_1 = c_4 O: | 3 c_1 = c_3 + 2 c_4 + 5 c_5 Sb: | c_2 = 2 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 = 10 c_2 = 2 c_3 = 5 c_4 = 10 c_5 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 10 HNO_3 + 2 Sb ⟶ 5 H_2O + 10 NO_2 + Sb_2O_5

+ ⟶ + +

nitric acid + gray antimony ⟶ water + nitrogen dioxide + antimony pentoxide

Construct the equilibrium constant, K, expression for: HNO_3 + Sb ⟶ H_2O + NO_2 + Sb_2O_5 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: 10 HNO_3 + 2 Sb ⟶ 5 H_2O + 10 NO_2 + Sb_2O_5 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 | 10 | -10 Sb | 2 | -2 H_2O | 5 | 5 NO_2 | 10 | 10 Sb_2O_5 | 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 | 10 | -10 | ([HNO3])^(-10) Sb | 2 | -2 | ([Sb])^(-2) H_2O | 5 | 5 | ([H2O])^5 NO_2 | 10 | 10 | ([NO2])^10 Sb_2O_5 | 1 | 1 | [Sb2O5] 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])^(-10) ([Sb])^(-2) ([H2O])^5 ([NO2])^10 [Sb2O5] = (([H2O])^5 ([NO2])^10 [Sb2O5])/(([HNO3])^10 ([Sb])^2)

Construct the rate of reaction expression for: HNO_3 + Sb ⟶ H_2O + NO_2 + Sb_2O_5 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: 10 HNO_3 + 2 Sb ⟶ 5 H_2O + 10 NO_2 + Sb_2O_5 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 | 10 | -10 Sb | 2 | -2 H_2O | 5 | 5 NO_2 | 10 | 10 Sb_2O_5 | 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 | 10 | -10 | -1/10 (Δ[HNO3])/(Δt) Sb | 2 | -2 | -1/2 (Δ[Sb])/(Δt) H_2O | 5 | 5 | 1/5 (Δ[H2O])/(Δt) NO_2 | 10 | 10 | 1/10 (Δ[NO2])/(Δt) Sb_2O_5 | 1 | 1 | (Δ[Sb2O5])/(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 = -1/10 (Δ[HNO3])/(Δt) = -1/2 (Δ[Sb])/(Δt) = 1/5 (Δ[H2O])/(Δt) = 1/10 (Δ[NO2])/(Δt) = (Δ[Sb2O5])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| nitric acid | gray antimony | water | nitrogen dioxide | antimony pentoxide formula | HNO_3 | Sb | H_2O | NO_2 | Sb_2O_5 Hill formula | HNO_3 | Sb | H_2O | NO_2 | O_5Sb_2 name | nitric acid | gray antimony | water | nitrogen dioxide | antimony pentoxide IUPAC name | nitric acid | antimony | water | Nitrogen dioxide |

| nitric acid | gray antimony | water | nitrogen dioxide | antimony pentoxide molar mass | 63.012 g/mol | 121.76 g/mol | 18.015 g/mol | 46.005 g/mol | 323.51 g/mol phase | liquid (at STP) | solid (at STP) | liquid (at STP) | gas (at STP) | solid (at STP) melting point | -41.6 °C | 630 °C | 0 °C | -11 °C | 380 °C boiling point | 83 °C | 1587 °C | 99.9839 °C | 21 °C | density | 1.5129 g/cm^3 | 6.69 g/cm^3 | 1 g/cm^3 | 0.00188 g/cm^3 (at 25 °C) | 3.78 g/cm^3 solubility in water | miscible | | | reacts | insoluble surface tension | | | 0.0728 N/m | | dynamic viscosity | 7.6×10^-4 Pa s (at 25 °C) | | 8.9×10^-4 Pa s (at 25 °C) | 4.02×10^-4 Pa s (at 25 °C) | odor | | | odorless | |