HNO2 = H2O + NO + NO2

HNO_2 nitrous acid ⟶ H_2O water + NO nitric oxide + NO_2 nitrogen dioxide

Balance the chemical equation algebraically: HNO_2 ⟶ H_2O + NO + NO_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 HNO_2 ⟶ c_2 H_2O + c_3 NO + c_4 NO_2 Set the number of atoms in the reactants equal to the number of atoms in the products for H, N and O: H: | c_1 = 2 c_2 N: | c_1 = c_3 + c_4 O: | 2 c_1 = c_2 + c_3 + 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 = 2 c_2 = 1 c_3 = 1 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 HNO_2 ⟶ H_2O + NO + NO_2

⟶ + +

nitrous acid ⟶ water + nitric oxide + nitrogen dioxide

Construct the equilibrium constant, K, expression for: HNO_2 ⟶ H_2O + NO + NO_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: 2 HNO_2 ⟶ H_2O + NO + NO_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 HNO_2 | 2 | -2 H_2O | 1 | 1 NO | 1 | 1 NO_2 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression HNO_2 | 2 | -2 | ([HNO2])^(-2) H_2O | 1 | 1 | [H2O] NO | 1 | 1 | [NO] NO_2 | 1 | 1 | [NO2] 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 = ([HNO2])^(-2) [H2O] [NO] [NO2] = ([H2O] [NO] [NO2])/([HNO2])^2

Construct the rate of reaction expression for: HNO_2 ⟶ H_2O + NO + NO_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: 2 HNO_2 ⟶ H_2O + NO + NO_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 HNO_2 | 2 | -2 H_2O | 1 | 1 NO | 1 | 1 NO_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 HNO_2 | 2 | -2 | -1/2 (Δ[HNO2])/(Δt) H_2O | 1 | 1 | (Δ[H2O])/(Δt) NO | 1 | 1 | (Δ[NO])/(Δt) NO_2 | 1 | 1 | (Δ[NO2])/(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 = -1/2 (Δ[HNO2])/(Δt) = (Δ[H2O])/(Δt) = (Δ[NO])/(Δt) = (Δ[NO2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| nitrous acid | water | nitric oxide | nitrogen dioxide formula | HNO_2 | H_2O | NO | NO_2 name | nitrous acid | water | nitric oxide | nitrogen dioxide IUPAC name | nitrous acid | water | nitric oxide | Nitrogen dioxide