H2O + SiF4 = H2SiO3 + H2SiF6

H_2O water + SiF_4 silicon tetrafluoride ⟶ H_2O_3Si metasilicic acid + H_2SiF_6 fluorosilicic acid

Balance the chemical equation algebraically: H_2O + SiF_4 ⟶ H_2O_3Si + H_2SiF_6 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2O + c_2 SiF_4 ⟶ c_3 H_2O_3Si + c_4 H_2SiF_6 Set the number of atoms in the reactants equal to the number of atoms in the products for H, O, F and Si: H: | 2 c_1 = 2 c_3 + 2 c_4 O: | c_1 = 3 c_3 F: | 4 c_2 = 6 c_4 Si: | c_2 = c_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_3 = 1 and solve the system of equations for the remaining coefficients: c_1 = 3 c_2 = 3 c_3 = 1 c_4 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 3 H_2O + 3 SiF_4 ⟶ H_2O_3Si + 2 H_2SiF_6

+ ⟶ +

water + silicon tetrafluoride ⟶ metasilicic acid + fluorosilicic acid

Construct the equilibrium constant, K, expression for: H_2O + SiF_4 ⟶ H_2O_3Si + H_2SiF_6 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 H_2O + 3 SiF_4 ⟶ H_2O_3Si + 2 H_2SiF_6 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_2O | 3 | -3 SiF_4 | 3 | -3 H_2O_3Si | 1 | 1 H_2SiF_6 | 2 | 2 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression H_2O | 3 | -3 | ([H2O])^(-3) SiF_4 | 3 | -3 | ([SiF4])^(-3) H_2O_3Si | 1 | 1 | [H2O3Si] H_2SiF_6 | 2 | 2 | ([H2SiF6])^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 = ([H2O])^(-3) ([SiF4])^(-3) [H2O3Si] ([H2SiF6])^2 = ([H2O3Si] ([H2SiF6])^2)/(([H2O])^3 ([SiF4])^3)

Construct the rate of reaction expression for: H_2O + SiF_4 ⟶ H_2O_3Si + H_2SiF_6 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 H_2O + 3 SiF_4 ⟶ H_2O_3Si + 2 H_2SiF_6 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_2O | 3 | -3 SiF_4 | 3 | -3 H_2O_3Si | 1 | 1 H_2SiF_6 | 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 H_2O | 3 | -3 | -1/3 (Δ[H2O])/(Δt) SiF_4 | 3 | -3 | -1/3 (Δ[SiF4])/(Δt) H_2O_3Si | 1 | 1 | (Δ[H2O3Si])/(Δt) H_2SiF_6 | 2 | 2 | 1/2 (Δ[H2SiF6])/(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[H2O])/(Δt) = -1/3 (Δ[SiF4])/(Δt) = (Δ[H2O3Si])/(Δt) = 1/2 (Δ[H2SiF6])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| water | silicon tetrafluoride | metasilicic acid | fluorosilicic acid formula | H_2O | SiF_4 | H_2O_3Si | H_2SiF_6 Hill formula | H_2O | F_4Si | H_2O_3Si | F_6H_2Si name | water | silicon tetrafluoride | metasilicic acid | fluorosilicic acid IUPAC name | water | tetrafluorosilane | dihydroxy-oxo-silane | tetrafluorosilane dihydrofluoride

| water | silicon tetrafluoride | metasilicic acid | fluorosilicic acid molar mass | 18.015 g/mol | 104.079 g/mol | 78.098 g/mol | 144.09 g/mol phase | liquid (at STP) | gas (at STP) | solid (at STP) | melting point | 0 °C | -90.2 °C | 1704 °C | boiling point | 99.9839 °C | -86 °C | | density | 1 g/cm^3 | 0.004254 g/cm^3 (at 25 °C) | 1 g/cm^3 | 1.22 g/cm^3 solubility in water | | decomposes | | surface tension | 0.0728 N/m | | | dynamic viscosity | 8.9×10^-4 Pa s (at 25 °C) | | | odor | odorless | | |