Na3PO4 + MgI2 = NaI + Mg3(PO4)2

Na_3PO_4 trisodium phosphate + MgI_2 magnesium iodide ⟶ NaI sodium iodide + Mg_3(PO_4)_2·5H_2O Trimagnesium diphosphate pentahydrate

Balance the chemical equation algebraically: Na_3PO_4 + MgI_2 ⟶ NaI + Mg_3(PO_4)_2·5H_2O Add stoichiometric coefficients, c_i, to the reactants and products: c_1 Na_3PO_4 + c_2 MgI_2 ⟶ c_3 NaI + c_4 Mg_3(PO_4)_2·5H_2O Set the number of atoms in the reactants equal to the number of atoms in the products for Na, O, P, I and Mg: Na: | 3 c_1 = c_3 O: | 4 c_1 = 8 c_4 P: | c_1 = 2 c_4 I: | 2 c_2 = c_3 Mg: | c_2 = 3 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_4 = 1 and solve the system of equations for the remaining coefficients: c_1 = 2 c_2 = 3 c_3 = 6 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 Na_3PO_4 + 3 MgI_2 ⟶ 6 NaI + Mg_3(PO_4)_2·5H_2O

+ ⟶ +

trisodium phosphate + magnesium iodide ⟶ sodium iodide + Trimagnesium diphosphate pentahydrate

Construct the equilibrium constant, K, expression for: Na_3PO_4 + MgI_2 ⟶ NaI + Mg_3(PO_4)_2·5H_2O 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 Na_3PO_4 + 3 MgI_2 ⟶ 6 NaI + Mg_3(PO_4)_2·5H_2O 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 Na_3PO_4 | 2 | -2 MgI_2 | 3 | -3 NaI | 6 | 6 Mg_3(PO_4)_2·5H_2O | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression Na_3PO_4 | 2 | -2 | ([Na3PO4])^(-2) MgI_2 | 3 | -3 | ([MgI2])^(-3) NaI | 6 | 6 | ([NaI])^6 Mg_3(PO_4)_2·5H_2O | 1 | 1 | [Mg3(PO4)2·5H2O] 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 = ([Na3PO4])^(-2) ([MgI2])^(-3) ([NaI])^6 [Mg3(PO4)2·5H2O] = (([NaI])^6 [Mg3(PO4)2·5H2O])/(([Na3PO4])^2 ([MgI2])^3)

Construct the rate of reaction expression for: Na_3PO_4 + MgI_2 ⟶ NaI + Mg_3(PO_4)_2·5H_2O 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 Na_3PO_4 + 3 MgI_2 ⟶ 6 NaI + Mg_3(PO_4)_2·5H_2O 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 Na_3PO_4 | 2 | -2 MgI_2 | 3 | -3 NaI | 6 | 6 Mg_3(PO_4)_2·5H_2O | 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 Na_3PO_4 | 2 | -2 | -1/2 (Δ[Na3PO4])/(Δt) MgI_2 | 3 | -3 | -1/3 (Δ[MgI2])/(Δt) NaI | 6 | 6 | 1/6 (Δ[NaI])/(Δt) Mg_3(PO_4)_2·5H_2O | 1 | 1 | (Δ[Mg3(PO4)2·5H2O])/(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[Na3PO4])/(Δt) = -1/3 (Δ[MgI2])/(Δt) = 1/6 (Δ[NaI])/(Δt) = (Δ[Mg3(PO4)2·5H2O])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| trisodium phosphate | magnesium iodide | sodium iodide | Trimagnesium diphosphate pentahydrate formula | Na_3PO_4 | MgI_2 | NaI | Mg_3(PO_4)_2·5H_2O Hill formula | Na_3O_4P | I_2Mg | INa | Mg_3O_8P_2 name | trisodium phosphate | magnesium iodide | sodium iodide | Trimagnesium diphosphate pentahydrate IUPAC name | trisodium phosphate | magnesium diiodide | sodium iodide | trimagnesium diphosphate

| trisodium phosphate | magnesium iodide | sodium iodide | Trimagnesium diphosphate pentahydrate molar mass | 163.94 g/mol | 278.114 g/mol | 149.89424 g/mol | 262.85 g/mol phase | solid (at STP) | solid (at STP) | solid (at STP) | solid (at STP) melting point | 75 °C | 637 °C | 661 °C | 1357 °C boiling point | | | 1300 °C | density | 2.536 g/cm^3 | 4.43 g/cm^3 | 3.67 g/cm^3 | solubility in water | soluble | | | insoluble dynamic viscosity | | | 0.0010446 Pa s (at 691 °C) | odor | odorless | odorless | |