HNO3 + Zn = H2O + NO + Zn(NO3)2

HNO_3 (nitric acid) + Zn (zinc) ⟶ H_2O (water) + NO (nitric oxide) + Zn(NO3)2

Balance the chemical equation algebraically: HNO_3 + Zn ⟶ H_2O + NO + Zn(NO3)2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 HNO_3 + c_2 Zn ⟶ c_3 H_2O + c_4 NO + c_5 Zn(NO3)2 Set the number of atoms in the reactants equal to the number of atoms in the products for H, N, O and Zn: H: | c_1 = 2 c_3 N: | c_1 = c_4 + 2 c_5 O: | 3 c_1 = c_3 + c_4 + 6 c_5 Zn: | c_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_4 = 1 and solve the system of equations for the remaining coefficients: c_1 = 4 c_2 = 3/2 c_3 = 2 c_4 = 1 c_5 = 3/2 Multiply by the least common denominator, 2, to eliminate fractional coefficients: c_1 = 8 c_2 = 3 c_3 = 4 c_4 = 2 c_5 = 3 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 8 HNO_3 + 3 Zn ⟶ 4 H_2O + 2 NO + 3 Zn(NO3)2

+ ⟶ + + Zn(NO3)2

nitric acid + zinc ⟶ water + nitric oxide + Zn(NO3)2

Construct the equilibrium constant, K, expression for: HNO_3 + Zn ⟶ H_2O + NO + Zn(NO3)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: 8 HNO_3 + 3 Zn ⟶ 4 H_2O + 2 NO + 3 Zn(NO3)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_3 | 8 | -8 Zn | 3 | -3 H_2O | 4 | 4 NO | 2 | 2 Zn(NO3)2 | 3 | 3 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression HNO_3 | 8 | -8 | ([HNO3])^(-8) Zn | 3 | -3 | ([Zn])^(-3) H_2O | 4 | 4 | ([H2O])^4 NO | 2 | 2 | ([NO])^2 Zn(NO3)2 | 3 | 3 | ([Zn(NO3)2])^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])^(-8) ([Zn])^(-3) ([H2O])^4 ([NO])^2 ([Zn(NO3)2])^3 = (([H2O])^4 ([NO])^2 ([Zn(NO3)2])^3)/(([HNO3])^8 ([Zn])^3)

Construct the rate of reaction expression for: HNO_3 + Zn ⟶ H_2O + NO + Zn(NO3)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: 8 HNO_3 + 3 Zn ⟶ 4 H_2O + 2 NO + 3 Zn(NO3)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_3 | 8 | -8 Zn | 3 | -3 H_2O | 4 | 4 NO | 2 | 2 Zn(NO3)2 | 3 | 3 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 | 8 | -8 | -1/8 (Δ[HNO3])/(Δt) Zn | 3 | -3 | -1/3 (Δ[Zn])/(Δt) H_2O | 4 | 4 | 1/4 (Δ[H2O])/(Δt) NO | 2 | 2 | 1/2 (Δ[NO])/(Δt) Zn(NO3)2 | 3 | 3 | 1/3 (Δ[Zn(NO3)2])/(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 = -1/8 (Δ[HNO3])/(Δt) = -1/3 (Δ[Zn])/(Δt) = 1/4 (Δ[H2O])/(Δt) = 1/2 (Δ[NO])/(Δt) = 1/3 (Δ[Zn(NO3)2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| nitric acid | zinc | water | nitric oxide | Zn(NO3)2 formula | HNO_3 | Zn | H_2O | NO | Zn(NO3)2 Hill formula | HNO_3 | Zn | H_2O | NO | N2O6Zn name | nitric acid | zinc | water | nitric oxide |