O2 + Si = SiO2

O_2 (oxygen) + Si (silicon) ⟶ SiO_2 (silicon dioxide)

Balance the chemical equation algebraically: O_2 + Si ⟶ SiO_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 O_2 + c_2 Si ⟶ c_3 SiO_2 Set the number of atoms in the reactants equal to the number of atoms in the products for O and Si: O: | 2 c_1 = 2 c_3 Si: | c_2 = c_3 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 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | O_2 + Si ⟶ SiO_2

+ ⟶

oxygen + silicon ⟶ silicon dioxide

| oxygen | silicon | silicon dioxide molecular enthalpy | 0 kJ/mol | 0 kJ/mol | -911 kJ/mol total enthalpy | 0 kJ/mol | 0 kJ/mol | -911 kJ/mol | H_initial = 0 kJ/mol | | H_final = -911 kJ/mol ΔH_rxn^0 | -911 kJ/mol - 0 kJ/mol = -911 kJ/mol (exothermic) | |

Construct the equilibrium constant, K, expression for: O_2 + Si ⟶ SiO_2 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: O_2 + Si ⟶ SiO_2 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 O_2 | 1 | -1 Si | 1 | -1 SiO_2 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression O_2 | 1 | -1 | ([O2])^(-1) Si | 1 | -1 | ([Si])^(-1) SiO_2 | 1 | 1 | [SiO2] 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 = ([O2])^(-1) ([Si])^(-1) [SiO2] = ([SiO2])/([O2] [Si])

Construct the rate of reaction expression for: O_2 + Si ⟶ SiO_2 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: O_2 + Si ⟶ SiO_2 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 O_2 | 1 | -1 Si | 1 | -1 SiO_2 | 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 O_2 | 1 | -1 | -(Δ[O2])/(Δt) Si | 1 | -1 | -(Δ[Si])/(Δt) SiO_2 | 1 | 1 | (Δ[SiO2])/(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 = -(Δ[O2])/(Δt) = -(Δ[Si])/(Δt) = (Δ[SiO2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| oxygen | silicon | silicon dioxide formula | O_2 | Si | SiO_2 Hill formula | O_2 | Si | O_2Si name | oxygen | silicon | silicon dioxide IUPAC name | molecular oxygen | silicon | dioxosilane

| oxygen | silicon | silicon dioxide molar mass | 31.998 g/mol | 28.085 g/mol | 60.083 g/mol phase | gas (at STP) | solid (at STP) | solid (at STP) melting point | -218 °C | 1410 °C | 1713 °C boiling point | -183 °C | 2355 °C | 2950 °C density | 0.001429 g/cm^3 (at 0 °C) | 2.33 g/cm^3 | 2.196 g/cm^3 solubility in water | | insoluble | insoluble surface tension | 0.01347 N/m | | dynamic viscosity | 2.055×10^-5 Pa s (at 25 °C) | | odor | odorless | | odorless