Zn + Br2 = ZnBr

Zn zinc + Br_2 bromine ⟶ ZnBr

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

+ ⟶ ZnBr

zinc + bromine ⟶ ZnBr

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

Construct the rate of reaction expression for: Zn + Br_2 ⟶ ZnBr 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 Zn + Br_2 ⟶ 2 ZnBr 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 Zn | 2 | -2 Br_2 | 1 | -1 ZnBr | 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 Zn | 2 | -2 | -1/2 (Δ[Zn])/(Δt) Br_2 | 1 | -1 | -(Δ[Br2])/(Δt) ZnBr | 2 | 2 | 1/2 (Δ[ZnBr])/(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[Zn])/(Δt) = -(Δ[Br2])/(Δt) = 1/2 (Δ[ZnBr])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| zinc | bromine | ZnBr formula | Zn | Br_2 | ZnBr Hill formula | Zn | Br_2 | BrZn name | zinc | bromine | IUPAC name | zinc | molecular bromine |

| zinc | bromine | ZnBr molar mass | 65.38 g/mol | 159.81 g/mol | 145.3 g/mol phase | solid (at STP) | liquid (at STP) | melting point | 420 °C | -7.2 °C | boiling point | 907 °C | 58.8 °C | density | 7.14 g/cm^3 | 3.119 g/cm^3 | solubility in water | insoluble | insoluble | surface tension | | 0.0409 N/m | dynamic viscosity | | 9.44×10^-4 Pa s (at 25 °C) | odor | odorless | |