Br2 + CF4 = F2 + CBr4

Br_2 bromine + CF_4 tetrafluoromethane ⟶ F_2 fluorine + CBr_4 carbon tetrabromide

Balance the chemical equation algebraically: Br_2 + CF_4 ⟶ F_2 + CBr_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 Br_2 + c_2 CF_4 ⟶ c_3 F_2 + c_4 CBr_4 Set the number of atoms in the reactants equal to the number of atoms in the products for Br, C and F: Br: | 2 c_1 = 4 c_4 C: | c_2 = c_4 F: | 4 c_2 = 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 = 2 c_2 = 1 c_3 = 2 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 Br_2 + CF_4 ⟶ 2 F_2 + CBr_4

+ ⟶ +

bromine + tetrafluoromethane ⟶ fluorine + carbon tetrabromide

| bromine | tetrafluoromethane | fluorine | carbon tetrabromide molecular enthalpy | 0 kJ/mol | -933.6 kJ/mol | 0 kJ/mol | 29.4 kJ/mol total enthalpy | 0 kJ/mol | -933.6 kJ/mol | 0 kJ/mol | 29.4 kJ/mol | H_initial = -933.6 kJ/mol | | H_final = 29.4 kJ/mol | ΔH_rxn^0 | 29.4 kJ/mol - -933.6 kJ/mol = 963 kJ/mol (endothermic) | | |

Construct the equilibrium constant, K, expression for: Br_2 + CF_4 ⟶ F_2 + CBr_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: 2 Br_2 + CF_4 ⟶ 2 F_2 + CBr_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 Br_2 | 2 | -2 CF_4 | 1 | -1 F_2 | 2 | 2 CBr_4 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression Br_2 | 2 | -2 | ([Br2])^(-2) CF_4 | 1 | -1 | ([CF4])^(-1) F_2 | 2 | 2 | ([F2])^2 CBr_4 | 1 | 1 | [CBr4] 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 = ([Br2])^(-2) ([CF4])^(-1) ([F2])^2 [CBr4] = (([F2])^2 [CBr4])/(([Br2])^2 [CF4])

Construct the rate of reaction expression for: Br_2 + CF_4 ⟶ F_2 + CBr_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: 2 Br_2 + CF_4 ⟶ 2 F_2 + CBr_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 Br_2 | 2 | -2 CF_4 | 1 | -1 F_2 | 2 | 2 CBr_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 Br_2 | 2 | -2 | -1/2 (Δ[Br2])/(Δt) CF_4 | 1 | -1 | -(Δ[CF4])/(Δt) F_2 | 2 | 2 | 1/2 (Δ[F2])/(Δt) CBr_4 | 1 | 1 | (Δ[CBr4])/(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[Br2])/(Δt) = -(Δ[CF4])/(Δt) = 1/2 (Δ[F2])/(Δt) = (Δ[CBr4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| bromine | tetrafluoromethane | fluorine | carbon tetrabromide formula | Br_2 | CF_4 | F_2 | CBr_4 name | bromine | tetrafluoromethane | fluorine | carbon tetrabromide IUPAC name | molecular bromine | tetrafluoromethane | molecular fluorine | carbon tetrabromide

| bromine | tetrafluoromethane | fluorine | carbon tetrabromide molar mass | 159.81 g/mol | 88.005 g/mol | 37.996806326 g/mol | 331.63 g/mol phase | liquid (at STP) | gas (at STP) | gas (at STP) | solid (at STP) melting point | -7.2 °C | -184 °C | -219.6 °C | 89 °C boiling point | 58.8 °C | -130 °C | -188.12 °C | 190 °C density | 3.119 g/cm^3 | | 0.001696 g/cm^3 (at 0 °C) | 3.42 g/cm^3 solubility in water | insoluble | insoluble | reacts | insoluble surface tension | 0.0409 N/m | | | dynamic viscosity | 9.44×10^-4 Pa s (at 25 °C) | 1.724×10^-5 Pa s (at 25 °C) | 2.344×10^-5 Pa s (at 25 °C) | 0.00244 Pa s (at 101 °C)