F2 + S8 = SF6

F_2 fluorine + S_8 rhombic sulfur ⟶ SF_6 sulfur hexafluoride

Balance the chemical equation algebraically: F_2 + S_8 ⟶ SF_6 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 F_2 + c_2 S_8 ⟶ c_3 SF_6 Set the number of atoms in the reactants equal to the number of atoms in the products for F and S: F: | 2 c_1 = 6 c_3 S: | 8 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_2 = 1 and solve the system of equations for the remaining coefficients: c_1 = 24 c_2 = 1 c_3 = 8 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 24 F_2 + S_8 ⟶ 8 SF_6

+ ⟶

fluorine + rhombic sulfur ⟶ sulfur hexafluoride

| fluorine | rhombic sulfur | sulfur hexafluoride molecular enthalpy | 0 kJ/mol | 0 kJ/mol | -1221 kJ/mol total enthalpy | 0 kJ/mol | 0 kJ/mol | -9764 kJ/mol | H_initial = 0 kJ/mol | | H_final = -9764 kJ/mol ΔH_rxn^0 | -9764 kJ/mol - 0 kJ/mol = -9764 kJ/mol (exothermic) | |

| fluorine | rhombic sulfur | sulfur hexafluoride molecular entropy | 202.8 J/(mol K) | 32.1 J/(mol K) | 292 J/(mol K) total entropy | 4867 J/(mol K) | 32.1 J/(mol K) | 2336 J/(mol K) | S_initial = 4899 J/(mol K) | | S_final = 2336 J/(mol K) ΔS_rxn^0 | 2336 J/(mol K) - 4899 J/(mol K) = -2563 J/(mol K) (exoentropic) | |

Construct the equilibrium constant, K, expression for: F_2 + S_8 ⟶ SF_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: 24 F_2 + S_8 ⟶ 8 SF_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 F_2 | 24 | -24 S_8 | 1 | -1 SF_6 | 8 | 8 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression F_2 | 24 | -24 | ([F2])^(-24) S_8 | 1 | -1 | ([S8])^(-1) SF_6 | 8 | 8 | ([SF6])^8 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 = ([F2])^(-24) ([S8])^(-1) ([SF6])^8 = ([SF6])^8/(([F2])^24 [S8])

Construct the rate of reaction expression for: F_2 + S_8 ⟶ SF_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: 24 F_2 + S_8 ⟶ 8 SF_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 F_2 | 24 | -24 S_8 | 1 | -1 SF_6 | 8 | 8 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 F_2 | 24 | -24 | -1/24 (Δ[F2])/(Δt) S_8 | 1 | -1 | -(Δ[S8])/(Δt) SF_6 | 8 | 8 | 1/8 (Δ[SF6])/(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 = -1/24 (Δ[F2])/(Δt) = -(Δ[S8])/(Δt) = 1/8 (Δ[SF6])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| fluorine | rhombic sulfur | sulfur hexafluoride formula | F_2 | S_8 | SF_6 Hill formula | F_2 | S_8 | F_6S name | fluorine | rhombic sulfur | sulfur hexafluoride IUPAC name | molecular fluorine | octathiocane |

| fluorine | rhombic sulfur | sulfur hexafluoride molar mass | 37.996806326 g/mol | 256.5 g/mol | 146.05 g/mol phase | gas (at STP) | solid (at STP) | gas (at STP) melting point | -219.6 °C | | -49.596 °C boiling point | -188.12 °C | | -63.8 °C density | 0.001696 g/cm^3 (at 0 °C) | 2.07 g/cm^3 | 0.00597 g/cm^3 (at 50 °C) solubility in water | reacts | | dynamic viscosity | 2.344×10^-5 Pa s (at 25 °C) | | 3.7204×10^-5 Pa s (at 627 °C) odor | | | odorless