H3PO4 + Na2SO3 = Na2PO4 + H3SO3

H_3PO_4 phosphoric acid + Na_2SO_3 sodium sulfite ⟶ Na2PO4 + H3SO3

Balance the chemical equation algebraically: H_3PO_4 + Na_2SO_3 ⟶ Na2PO4 + H3SO3 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_3PO_4 + c_2 Na_2SO_3 ⟶ c_3 Na2PO4 + c_4 H3SO3 Set the number of atoms in the reactants equal to the number of atoms in the products for H, O, P, Na and S: H: | 3 c_1 = 3 c_4 O: | 4 c_1 + 3 c_2 = 4 c_3 + 3 c_4 P: | c_1 = c_3 Na: | 2 c_2 = 2 c_3 S: | 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_1 = 1 and solve the system of equations for the remaining coefficients: c_1 = 1 c_2 = 1 c_3 = 1 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | H_3PO_4 + Na_2SO_3 ⟶ Na2PO4 + H3SO3

+ ⟶ Na2PO4 + H3SO3

phosphoric acid + sodium sulfite ⟶ Na2PO4 + H3SO3

Construct the equilibrium constant, K, expression for: H_3PO_4 + Na_2SO_3 ⟶ Na2PO4 + H3SO3 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: H_3PO_4 + Na_2SO_3 ⟶ Na2PO4 + H3SO3 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 H_3PO_4 | 1 | -1 Na_2SO_3 | 1 | -1 Na2PO4 | 1 | 1 H3SO3 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression H_3PO_4 | 1 | -1 | ([H3PO4])^(-1) Na_2SO_3 | 1 | -1 | ([Na2SO3])^(-1) Na2PO4 | 1 | 1 | [Na2PO4] H3SO3 | 1 | 1 | [H3SO3] 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 = ([H3PO4])^(-1) ([Na2SO3])^(-1) [Na2PO4] [H3SO3] = ([Na2PO4] [H3SO3])/([H3PO4] [Na2SO3])

Construct the rate of reaction expression for: H_3PO_4 + Na_2SO_3 ⟶ Na2PO4 + H3SO3 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: H_3PO_4 + Na_2SO_3 ⟶ Na2PO4 + H3SO3 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 H_3PO_4 | 1 | -1 Na_2SO_3 | 1 | -1 Na2PO4 | 1 | 1 H3SO3 | 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 H_3PO_4 | 1 | -1 | -(Δ[H3PO4])/(Δt) Na_2SO_3 | 1 | -1 | -(Δ[Na2SO3])/(Δt) Na2PO4 | 1 | 1 | (Δ[Na2PO4])/(Δt) H3SO3 | 1 | 1 | (Δ[H3SO3])/(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 = -(Δ[H3PO4])/(Δt) = -(Δ[Na2SO3])/(Δt) = (Δ[Na2PO4])/(Δt) = (Δ[H3SO3])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| phosphoric acid | sodium sulfite | Na2PO4 | H3SO3 formula | H_3PO_4 | Na_2SO_3 | Na2PO4 | H3SO3 Hill formula | H_3O_4P | Na_2O_3S | Na2O4P | H3O3S name | phosphoric acid | sodium sulfite | | IUPAC name | phosphoric acid | disodium sulfite | |

| phosphoric acid | sodium sulfite | Na2PO4 | H3SO3 molar mass | 97.994 g/mol | 126.04 g/mol | 140.95 g/mol | 83.08 g/mol phase | liquid (at STP) | solid (at STP) | | melting point | 42.4 °C | 500 °C | | boiling point | 158 °C | | | density | 1.685 g/cm^3 | 2.63 g/cm^3 | | solubility in water | very soluble | | | odor | odorless | | |