NaOH + Si = H2 + Na4SiO4

NaOH sodium hydroxide + Si silicon ⟶ H_2 hydrogen + Na_4O_4Si sodium silicate

Balance the chemical equation algebraically: NaOH + Si ⟶ H_2 + Na_4O_4Si Add stoichiometric coefficients, c_i, to the reactants and products: c_1 NaOH + c_2 Si ⟶ c_3 H_2 + c_4 Na_4O_4Si Set the number of atoms in the reactants equal to the number of atoms in the products for H, Na, O and Si: H: | c_1 = 2 c_3 Na: | c_1 = 4 c_4 O: | c_1 = 4 c_4 Si: | 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 = 4 c_2 = 1 c_3 = 2 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 4 NaOH + Si ⟶ 2 H_2 + Na_4O_4Si

+ ⟶ +

sodium hydroxide + silicon ⟶ hydrogen + sodium silicate

Construct the equilibrium constant, K, expression for: NaOH + Si ⟶ H_2 + Na_4O_4Si 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: 4 NaOH + Si ⟶ 2 H_2 + Na_4O_4Si 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 NaOH | 4 | -4 Si | 1 | -1 H_2 | 2 | 2 Na_4O_4Si | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression NaOH | 4 | -4 | ([NaOH])^(-4) Si | 1 | -1 | ([Si])^(-1) H_2 | 2 | 2 | ([H2])^2 Na_4O_4Si | 1 | 1 | [Na4O4Si] 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 = ([NaOH])^(-4) ([Si])^(-1) ([H2])^2 [Na4O4Si] = (([H2])^2 [Na4O4Si])/(([NaOH])^4 [Si])

Construct the rate of reaction expression for: NaOH + Si ⟶ H_2 + Na_4O_4Si 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: 4 NaOH + Si ⟶ 2 H_2 + Na_4O_4Si 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 NaOH | 4 | -4 Si | 1 | -1 H_2 | 2 | 2 Na_4O_4Si | 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 NaOH | 4 | -4 | -1/4 (Δ[NaOH])/(Δt) Si | 1 | -1 | -(Δ[Si])/(Δt) H_2 | 2 | 2 | 1/2 (Δ[H2])/(Δt) Na_4O_4Si | 1 | 1 | (Δ[Na4O4Si])/(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 = -1/4 (Δ[NaOH])/(Δt) = -(Δ[Si])/(Δt) = 1/2 (Δ[H2])/(Δt) = (Δ[Na4O4Si])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| sodium hydroxide | silicon | hydrogen | sodium silicate formula | NaOH | Si | H_2 | Na_4O_4Si Hill formula | HNaO | Si | H_2 | Na_4O_4Si_1 name | sodium hydroxide | silicon | hydrogen | sodium silicate IUPAC name | sodium hydroxide | silicon | molecular hydrogen |

| sodium hydroxide | silicon | hydrogen | sodium silicate molar mass | 39.997 g/mol | 28.085 g/mol | 2.016 g/mol | 184.04 g/mol phase | solid (at STP) | solid (at STP) | gas (at STP) | melting point | 323 °C | 1410 °C | -259.2 °C | boiling point | 1390 °C | 2355 °C | -252.8 °C | density | 2.13 g/cm^3 | 2.33 g/cm^3 | 8.99×10^-5 g/cm^3 (at 0 °C) | 1.37 g/cm^3 solubility in water | soluble | insoluble | | slightly soluble surface tension | 0.07435 N/m | | | dynamic viscosity | 0.004 Pa s (at 350 °C) | | 8.9×10^-6 Pa s (at 25 °C) | 1 Pa s (at 1088 °C) odor | | | odorless |