NaH = H2 + Na

NaH sodium hydride ⟶ H_2 hydrogen + Na sodium

Balance the chemical equation algebraically: NaH ⟶ H_2 + Na Add stoichiometric coefficients, c_i, to the reactants and products: c_1 NaH ⟶ c_2 H_2 + c_3 Na Set the number of atoms in the reactants equal to the number of atoms in the products for H and Na: H: | c_1 = 2 c_2 Na: | c_1 = 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_2 = 1 and solve the system of equations for the remaining coefficients: c_1 = 2 c_2 = 1 c_3 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 NaH ⟶ H_2 + 2 Na

⟶ +

sodium hydride ⟶ hydrogen + sodium

| sodium hydride | hydrogen | sodium molecular enthalpy | -56.3 kJ/mol | 0 kJ/mol | 0 kJ/mol total enthalpy | -112.6 kJ/mol | 0 kJ/mol | 0 kJ/mol | H_initial = -112.6 kJ/mol | H_final = 0 kJ/mol | ΔH_rxn^0 | 0 kJ/mol - -112.6 kJ/mol = 112.6 kJ/mol (endothermic) | |

| sodium hydride | hydrogen | sodium molecular entropy | 40 J/(mol K) | 115 J/(mol K) | 51 J/(mol K) total entropy | 80 J/(mol K) | 115 J/(mol K) | 102 J/(mol K) | S_initial = 80 J/(mol K) | S_final = 217 J/(mol K) | ΔS_rxn^0 | 217 J/(mol K) - 80 J/(mol K) = 137 J/(mol K) (endoentropic) | |

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

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

| sodium hydride | hydrogen | sodium formula | NaH | H_2 | Na Hill formula | HNa | H_2 | Na name | sodium hydride | hydrogen | sodium IUPAC name | sodium hydride | molecular hydrogen | sodium

| sodium hydride | hydrogen | sodium molar mass | 23.998 g/mol | 2.016 g/mol | 22.98976928 g/mol phase | solid (at STP) | gas (at STP) | solid (at STP) melting point | 800 °C | -259.2 °C | 97.8 °C boiling point | | -252.8 °C | 883 °C density | | 8.99×10^-5 g/cm^3 (at 0 °C) | 0.968 g/cm^3 solubility in water | | | decomposes dynamic viscosity | | 8.9×10^-6 Pa s (at 25 °C) | 1.413×10^-5 Pa s (at 527 °C) odor | | odorless |