NaCl + H3PO4 = HCl + Na3PO4

NaCl sodium chloride + H_3PO_4 phosphoric acid ⟶ HCl hydrogen chloride + Na_3PO_4 trisodium phosphate

Balance the chemical equation algebraically: NaCl + H_3PO_4 ⟶ HCl + Na_3PO_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 NaCl + c_2 H_3PO_4 ⟶ c_3 HCl + c_4 Na_3PO_4 Set the number of atoms in the reactants equal to the number of atoms in the products for Cl, Na, H, O and P: Cl: | c_1 = c_3 Na: | c_1 = 3 c_4 H: | 3 c_2 = c_3 O: | 4 c_2 = 4 c_4 P: | 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 = 3 c_2 = 1 c_3 = 3 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 3 NaCl + H_3PO_4 ⟶ 3 HCl + Na_3PO_4

+ ⟶ +

sodium chloride + phosphoric acid ⟶ hydrogen chloride + trisodium phosphate

Construct the equilibrium constant, K, expression for: NaCl + H_3PO_4 ⟶ HCl + Na_3PO_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: 3 NaCl + H_3PO_4 ⟶ 3 HCl + Na_3PO_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 NaCl | 3 | -3 H_3PO_4 | 1 | -1 HCl | 3 | 3 Na_3PO_4 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression NaCl | 3 | -3 | ([NaCl])^(-3) H_3PO_4 | 1 | -1 | ([H3PO4])^(-1) HCl | 3 | 3 | ([HCl])^3 Na_3PO_4 | 1 | 1 | [Na3PO4] 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 = ([NaCl])^(-3) ([H3PO4])^(-1) ([HCl])^3 [Na3PO4] = (([HCl])^3 [Na3PO4])/(([NaCl])^3 [H3PO4])

Construct the rate of reaction expression for: NaCl + H_3PO_4 ⟶ HCl + Na_3PO_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: 3 NaCl + H_3PO_4 ⟶ 3 HCl + Na_3PO_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 NaCl | 3 | -3 H_3PO_4 | 1 | -1 HCl | 3 | 3 Na_3PO_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 NaCl | 3 | -3 | -1/3 (Δ[NaCl])/(Δt) H_3PO_4 | 1 | -1 | -(Δ[H3PO4])/(Δt) HCl | 3 | 3 | 1/3 (Δ[HCl])/(Δt) Na_3PO_4 | 1 | 1 | (Δ[Na3PO4])/(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 = -1/3 (Δ[NaCl])/(Δt) = -(Δ[H3PO4])/(Δt) = 1/3 (Δ[HCl])/(Δt) = (Δ[Na3PO4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| sodium chloride | phosphoric acid | hydrogen chloride | trisodium phosphate formula | NaCl | H_3PO_4 | HCl | Na_3PO_4 Hill formula | ClNa | H_3O_4P | ClH | Na_3O_4P name | sodium chloride | phosphoric acid | hydrogen chloride | trisodium phosphate

| sodium chloride | phosphoric acid | hydrogen chloride | trisodium phosphate molar mass | 58.44 g/mol | 97.994 g/mol | 36.46 g/mol | 163.94 g/mol phase | solid (at STP) | liquid (at STP) | gas (at STP) | solid (at STP) melting point | 801 °C | 42.4 °C | -114.17 °C | 75 °C boiling point | 1413 °C | 158 °C | -85 °C | density | 2.16 g/cm^3 | 1.685 g/cm^3 | 0.00149 g/cm^3 (at 25 °C) | 2.536 g/cm^3 solubility in water | soluble | very soluble | miscible | soluble odor | odorless | odorless | | odorless