CH3CH = CH2

CH_2=CH_2 ethylene ⟶ CH2

Balance the chemical equation algebraically: CH_2=CH_2 ⟶ CH2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 CH_2=CH_2 ⟶ c_2 CH2 Set the number of atoms in the reactants equal to the number of atoms in the products for C and H: C: | 2 c_1 = c_2 H: | 4 c_1 = 2 c_2 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 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | CH_2=CH_2 ⟶ 2 CH2

⟶ CH2

ethylene ⟶ CH2

Construct the equilibrium constant, K, expression for: CH_2=CH_2 ⟶ CH2 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: CH_2=CH_2 ⟶ 2 CH2 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 CH_2=CH_2 | 1 | -1 CH2 | 2 | 2 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression CH_2=CH_2 | 1 | -1 | ([CH2=CH2])^(-1) CH2 | 2 | 2 | ([CH2])^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 = ([CH2=CH2])^(-1) ([CH2])^2 = ([CH2])^2/([CH2=CH2])

Construct the rate of reaction expression for: CH_2=CH_2 ⟶ CH2 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: CH_2=CH_2 ⟶ 2 CH2 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 CH_2=CH_2 | 1 | -1 CH2 | 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 CH_2=CH_2 | 1 | -1 | -(Δ[CH2=CH2])/(Δt) CH2 | 2 | 2 | 1/2 (Δ[CH2])/(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[CH2=CH2])/(Δt) = 1/2 (Δ[CH2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| ethylene | CH2 formula | CH_2=CH_2 | CH2 Hill formula | C_2H_4 | CH2 name | ethylene |

| ethylene | CH2 molar mass | 28.054 g/mol | 14.027 g/mol phase | gas (at STP) | melting point | -169 °C | boiling point | -104 °C | density | 1.153 g/cm^3 (at 25 °C) | solubility in water | insoluble | surface tension | 0.0181 N/m | dynamic viscosity | 1.034×10^-5 Pa s (at 25 °C) |