Ca + ZnCl2 = Zn + CaCl2

Ca calcium + ZnCl_2 zinc chloride ⟶ Zn zinc + CaCl_2 calcium chloride

Balance the chemical equation algebraically: Ca + ZnCl_2 ⟶ Zn + CaCl_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 Ca + c_2 ZnCl_2 ⟶ c_3 Zn + c_4 CaCl_2 Set the number of atoms in the reactants equal to the number of atoms in the products for Ca, Cl and Zn: Ca: | c_1 = c_4 Cl: | 2 c_2 = 2 c_4 Zn: | 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_1 = 1 and solve the system of equations for the remaining coefficients: c_1 = 1 c_2 = 1 c_3 = 1 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | Ca + ZnCl_2 ⟶ Zn + CaCl_2

+ ⟶ +

calcium + zinc chloride ⟶ zinc + calcium chloride

| calcium | zinc chloride | zinc | calcium chloride molecular enthalpy | 0 kJ/mol | -415.1 kJ/mol | 0 kJ/mol | -795.4 kJ/mol total enthalpy | 0 kJ/mol | -415.1 kJ/mol | 0 kJ/mol | -795.4 kJ/mol | H_initial = -415.1 kJ/mol | | H_final = -795.4 kJ/mol | ΔH_rxn^0 | -795.4 kJ/mol - -415.1 kJ/mol = -380.3 kJ/mol (exothermic) | | |

Construct the equilibrium constant, K, expression for: Ca + ZnCl_2 ⟶ Zn + CaCl_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: Ca + ZnCl_2 ⟶ Zn + CaCl_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 Ca | 1 | -1 ZnCl_2 | 1 | -1 Zn | 1 | 1 CaCl_2 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression Ca | 1 | -1 | ([Ca])^(-1) ZnCl_2 | 1 | -1 | ([ZnCl2])^(-1) Zn | 1 | 1 | [Zn] CaCl_2 | 1 | 1 | [CaCl2] 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 = ([Ca])^(-1) ([ZnCl2])^(-1) [Zn] [CaCl2] = ([Zn] [CaCl2])/([Ca] [ZnCl2])

Construct the rate of reaction expression for: Ca + ZnCl_2 ⟶ Zn + CaCl_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: Ca + ZnCl_2 ⟶ Zn + CaCl_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 Ca | 1 | -1 ZnCl_2 | 1 | -1 Zn | 1 | 1 CaCl_2 | 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 Ca | 1 | -1 | -(Δ[Ca])/(Δt) ZnCl_2 | 1 | -1 | -(Δ[ZnCl2])/(Δt) Zn | 1 | 1 | (Δ[Zn])/(Δt) CaCl_2 | 1 | 1 | (Δ[CaCl2])/(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[Ca])/(Δt) = -(Δ[ZnCl2])/(Δt) = (Δ[Zn])/(Δt) = (Δ[CaCl2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| calcium | zinc chloride | zinc | calcium chloride formula | Ca | ZnCl_2 | Zn | CaCl_2 Hill formula | Ca | Cl_2Zn | Zn | CaCl_2 name | calcium | zinc chloride | zinc | calcium chloride IUPAC name | calcium | zinc dichloride | zinc | calcium dichloride

| calcium | zinc chloride | zinc | calcium chloride molar mass | 40.078 g/mol | 136.3 g/mol | 65.38 g/mol | 111 g/mol phase | solid (at STP) | solid (at STP) | solid (at STP) | solid (at STP) melting point | 850 °C | 293 °C | 420 °C | 772 °C boiling point | 1484 °C | | 907 °C | density | 1.54 g/cm^3 | | 7.14 g/cm^3 | 2.15 g/cm^3 solubility in water | decomposes | soluble | insoluble | soluble odor | | odorless | odorless |