Fe + H3PO4 = H2 + FePO4

Fe iron + H_3PO_4 phosphoric acid ⟶ H_2 hydrogen + FePO_4 iron(III) phosphate

Balance the chemical equation algebraically: Fe + H_3PO_4 ⟶ H_2 + FePO_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 Fe + c_2 H_3PO_4 ⟶ c_3 H_2 + c_4 FePO_4 Set the number of atoms in the reactants equal to the number of atoms in the products for Fe, H, O and P: Fe: | c_1 = c_4 H: | 3 c_2 = 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_1 = 1 and solve the system of equations for the remaining coefficients: c_1 = 1 c_2 = 1 c_3 = 3/2 c_4 = 1 Multiply by the least common denominator, 2, to eliminate fractional coefficients: c_1 = 2 c_2 = 2 c_3 = 3 c_4 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 Fe + 2 H_3PO_4 ⟶ 3 H_2 + 2 FePO_4

+ ⟶ +

iron + phosphoric acid ⟶ hydrogen + iron(III) phosphate

Construct the equilibrium constant, K, expression for: Fe + H_3PO_4 ⟶ H_2 + FePO_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: 2 Fe + 2 H_3PO_4 ⟶ 3 H_2 + 2 FePO_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 Fe | 2 | -2 H_3PO_4 | 2 | -2 H_2 | 3 | 3 FePO_4 | 2 | 2 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression Fe | 2 | -2 | ([Fe])^(-2) H_3PO_4 | 2 | -2 | ([H3PO4])^(-2) H_2 | 3 | 3 | ([H2])^3 FePO_4 | 2 | 2 | ([FePO4])^2 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 = ([Fe])^(-2) ([H3PO4])^(-2) ([H2])^3 ([FePO4])^2 = (([H2])^3 ([FePO4])^2)/(([Fe])^2 ([H3PO4])^2)

Construct the rate of reaction expression for: Fe + H_3PO_4 ⟶ H_2 + FePO_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: 2 Fe + 2 H_3PO_4 ⟶ 3 H_2 + 2 FePO_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 Fe | 2 | -2 H_3PO_4 | 2 | -2 H_2 | 3 | 3 FePO_4 | 2 | 2 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 Fe | 2 | -2 | -1/2 (Δ[Fe])/(Δt) H_3PO_4 | 2 | -2 | -1/2 (Δ[H3PO4])/(Δt) H_2 | 3 | 3 | 1/3 (Δ[H2])/(Δt) FePO_4 | 2 | 2 | 1/2 (Δ[FePO4])/(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[Fe])/(Δt) = -1/2 (Δ[H3PO4])/(Δt) = 1/3 (Δ[H2])/(Δt) = 1/2 (Δ[FePO4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| iron | phosphoric acid | hydrogen | iron(III) phosphate formula | Fe | H_3PO_4 | H_2 | FePO_4 Hill formula | Fe | H_3O_4P | H_2 | FeO_4P name | iron | phosphoric acid | hydrogen | iron(III) phosphate IUPAC name | iron | phosphoric acid | molecular hydrogen | iron(+3) cation phosphate

| iron | phosphoric acid | hydrogen | iron(III) phosphate molar mass | 55.845 g/mol | 97.994 g/mol | 2.016 g/mol | 150.81 g/mol phase | solid (at STP) | liquid (at STP) | gas (at STP) | melting point | 1535 °C | 42.4 °C | -259.2 °C | boiling point | 2750 °C | 158 °C | -252.8 °C | density | 7.874 g/cm^3 | 1.685 g/cm^3 | 8.99×10^-5 g/cm^3 (at 0 °C) | 2.87 g/cm^3 solubility in water | insoluble | very soluble | | dynamic viscosity | | | 8.9×10^-6 Pa s (at 25 °C) | odor | | odorless | odorless |