H2O + Ca2Si = Ca(OH)2 + SiH4

H_2O water + Ca2Si ⟶ Ca(OH)_2 calcium hydroxide + SiH_4 silane

Balance the chemical equation algebraically: H_2O + Ca2Si ⟶ Ca(OH)_2 + SiH_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2O + c_2 Ca2Si ⟶ c_3 Ca(OH)_2 + c_4 SiH_4 Set the number of atoms in the reactants equal to the number of atoms in the products for H, O, Ca and Si: H: | 2 c_1 = 2 c_3 + 4 c_4 O: | c_1 = 2 c_3 Ca: | 2 c_2 = c_3 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 H_2O + Ca2Si ⟶ 2 Ca(OH)_2 + SiH_4

+ Ca2Si ⟶ +

water + Ca2Si ⟶ calcium hydroxide + silane

Construct the equilibrium constant, K, expression for: H_2O + Ca2Si ⟶ Ca(OH)_2 + SiH_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: 4 H_2O + Ca2Si ⟶ 2 Ca(OH)_2 + SiH_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 H_2O | 4 | -4 Ca2Si | 1 | -1 Ca(OH)_2 | 2 | 2 SiH_4 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression H_2O | 4 | -4 | ([H2O])^(-4) Ca2Si | 1 | -1 | ([Ca2Si])^(-1) Ca(OH)_2 | 2 | 2 | ([Ca(OH)2])^2 SiH_4 | 1 | 1 | [SiH4] 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])^(-4) ([Ca2Si])^(-1) ([Ca(OH)2])^2 [SiH4] = (([Ca(OH)2])^2 [SiH4])/(([H2O])^4 [Ca2Si])

Construct the rate of reaction expression for: H_2O + Ca2Si ⟶ Ca(OH)_2 + SiH_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: 4 H_2O + Ca2Si ⟶ 2 Ca(OH)_2 + SiH_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 H_2O | 4 | -4 Ca2Si | 1 | -1 Ca(OH)_2 | 2 | 2 SiH_4 | 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 H_2O | 4 | -4 | -1/4 (Δ[H2O])/(Δt) Ca2Si | 1 | -1 | -(Δ[Ca2Si])/(Δt) Ca(OH)_2 | 2 | 2 | 1/2 (Δ[Ca(OH)2])/(Δt) SiH_4 | 1 | 1 | (Δ[SiH4])/(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[H2O])/(Δt) = -(Δ[Ca2Si])/(Δt) = 1/2 (Δ[Ca(OH)2])/(Δt) = (Δ[SiH4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| water | Ca2Si | calcium hydroxide | silane formula | H_2O | Ca2Si | Ca(OH)_2 | SiH_4 Hill formula | H_2O | Ca2Si | CaH_2O_2 | H_4Si name | water | | calcium hydroxide | silane IUPAC name | water | | calcium dihydroxide | silane

| water | Ca2Si | calcium hydroxide | silane molar mass | 18.015 g/mol | 108.24 g/mol | 74.092 g/mol | 32.117 g/mol phase | liquid (at STP) | | solid (at STP) | gas (at STP) melting point | 0 °C | | 550 °C | -185 °C boiling point | 99.9839 °C | | | -112 °C density | 1 g/cm^3 | | 2.24 g/cm^3 | 0.001313 g/cm^3 (at 25 °C) solubility in water | | | slightly soluble | surface tension | 0.0728 N/m | | | dynamic viscosity | 8.9×10^-4 Pa s (at 25 °C) | | | odor | odorless | | odorless |