Zn + HCl2 = H2 + ZnCl2

Zn zinc + HCl2 ⟶ H_2 hydrogen + ZnCl_2 zinc chloride

Balance the chemical equation algebraically: Zn + HCl2 ⟶ H_2 + ZnCl_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 Zn + c_2 HCl2 ⟶ c_3 H_2 + c_4 ZnCl_2 Set the number of atoms in the reactants equal to the number of atoms in the products for Zn, H and Cl: Zn: | c_1 = c_4 H: | c_2 = 2 c_3 Cl: | 2 c_2 = 2 c_4 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_3 = 1 and solve the system of equations for the remaining coefficients: c_1 = 2 c_2 = 2 c_3 = 1 c_4 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 Zn + 2 HCl2 ⟶ H_2 + 2 ZnCl_2

+ HCl2 ⟶ +

zinc + HCl2 ⟶ hydrogen + zinc chloride

Construct the equilibrium constant, K, expression for: Zn + HCl2 ⟶ H_2 + ZnCl_2 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 + 2 HCl2 ⟶ H_2 + 2 ZnCl_2 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 HCl2 | 2 | -2 H_2 | 1 | 1 ZnCl_2 | 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) HCl2 | 2 | -2 | ([HCl2])^(-2) H_2 | 1 | 1 | [H2] ZnCl_2 | 2 | 2 | ([ZnCl2])^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) ([HCl2])^(-2) [H2] ([ZnCl2])^2 = ([H2] ([ZnCl2])^2)/(([Zn])^2 ([HCl2])^2)

Construct the rate of reaction expression for: Zn + HCl2 ⟶ H_2 + ZnCl_2 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 + 2 HCl2 ⟶ H_2 + 2 ZnCl_2 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 HCl2 | 2 | -2 H_2 | 1 | 1 ZnCl_2 | 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) HCl2 | 2 | -2 | -1/2 (Δ[HCl2])/(Δt) H_2 | 1 | 1 | (Δ[H2])/(Δt) ZnCl_2 | 2 | 2 | 1/2 (Δ[ZnCl2])/(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) = -1/2 (Δ[HCl2])/(Δt) = (Δ[H2])/(Δt) = 1/2 (Δ[ZnCl2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| zinc | HCl2 | hydrogen | zinc chloride formula | Zn | HCl2 | H_2 | ZnCl_2 Hill formula | Zn | HCl2 | H_2 | Cl_2Zn name | zinc | | hydrogen | zinc chloride IUPAC name | zinc | | molecular hydrogen | zinc dichloride

| zinc | HCl2 | hydrogen | zinc chloride molar mass | 65.38 g/mol | 71.91 g/mol | 2.016 g/mol | 136.3 g/mol phase | solid (at STP) | | gas (at STP) | solid (at STP) melting point | 420 °C | | -259.2 °C | 293 °C boiling point | 907 °C | | -252.8 °C | density | 7.14 g/cm^3 | | 8.99×10^-5 g/cm^3 (at 0 °C) | solubility in water | insoluble | | | soluble dynamic viscosity | | | 8.9×10^-6 Pa s (at 25 °C) | odor | odorless | | odorless | odorless