NaNO3 + K2Se = NaNO2 + K2SeO4

NaNO_3 sodium nitrate + K_2Se potassium selenide ⟶ NaNO_2 sodium nitrite + K_2SeO_4 potassium selenate

Balance the chemical equation algebraically: NaNO_3 + K_2Se ⟶ NaNO_2 + K_2SeO_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 NaNO_3 + c_2 K_2Se ⟶ c_3 NaNO_2 + c_4 K_2SeO_4 Set the number of atoms in the reactants equal to the number of atoms in the products for N, Na, O, K and Se: N: | c_1 = c_3 Na: | c_1 = c_3 O: | 3 c_1 = 2 c_3 + 4 c_4 K: | 2 c_2 = 2 c_4 Se: | c_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 = 4 c_2 = 1 c_3 = 4 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 4 NaNO_3 + K_2Se ⟶ 4 NaNO_2 + K_2SeO_4

+ ⟶ +

sodium nitrate + potassium selenide ⟶ sodium nitrite + potassium selenate

Construct the equilibrium constant, K, expression for: NaNO_3 + K_2Se ⟶ NaNO_2 + K_2SeO_4 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 NaNO_3 + K_2Se ⟶ 4 NaNO_2 + K_2SeO_4 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 NaNO_3 | 4 | -4 K_2Se | 1 | -1 NaNO_2 | 4 | 4 K_2SeO_4 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression NaNO_3 | 4 | -4 | ([NaNO3])^(-4) K_2Se | 1 | -1 | ([K2Se])^(-1) NaNO_2 | 4 | 4 | ([NaNO2])^4 K_2SeO_4 | 1 | 1 | [K2SeO4] 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 = ([NaNO3])^(-4) ([K2Se])^(-1) ([NaNO2])^4 [K2SeO4] = (([NaNO2])^4 [K2SeO4])/(([NaNO3])^4 [K2Se])

Construct the rate of reaction expression for: NaNO_3 + K_2Se ⟶ NaNO_2 + K_2SeO_4 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 NaNO_3 + K_2Se ⟶ 4 NaNO_2 + K_2SeO_4 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 NaNO_3 | 4 | -4 K_2Se | 1 | -1 NaNO_2 | 4 | 4 K_2SeO_4 | 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 NaNO_3 | 4 | -4 | -1/4 (Δ[NaNO3])/(Δt) K_2Se | 1 | -1 | -(Δ[K2Se])/(Δt) NaNO_2 | 4 | 4 | 1/4 (Δ[NaNO2])/(Δt) K_2SeO_4 | 1 | 1 | (Δ[K2SeO4])/(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[NaNO3])/(Δt) = -(Δ[K2Se])/(Δt) = 1/4 (Δ[NaNO2])/(Δt) = (Δ[K2SeO4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| sodium nitrate | potassium selenide | sodium nitrite | potassium selenate formula | NaNO_3 | K_2Se | NaNO_2 | K_2SeO_4 Hill formula | NNaO_3 | K_2Se | NNaO_2 | K_2O_4Se name | sodium nitrate | potassium selenide | sodium nitrite | potassium selenate IUPAC name | sodium nitrate | dipotassium selenium(-2) anion | sodium nitrite |

| sodium nitrate | potassium selenide | sodium nitrite | potassium selenate molar mass | 84.994 g/mol | 157.17 g/mol | 68.995 g/mol | 221.16 g/mol phase | solid (at STP) | solid (at STP) | solid (at STP) | melting point | 306 °C | 800 °C | 271 °C | density | 2.26 g/cm^3 | 2.29 g/cm^3 | 2.168 g/cm^3 | 3.07 g/cm^3 solubility in water | soluble | | | dynamic viscosity | 0.003 Pa s (at 250 °C) | | |