KI + HgI2 = K2HgI4

KI potassium iodide + HgI_2 mercury(II) iodide ⟶ K_2HgI_4 mercury potassium iodide

Balance the chemical equation algebraically: KI + HgI_2 ⟶ K_2HgI_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 KI + c_2 HgI_2 ⟶ c_3 K_2HgI_4 Set the number of atoms in the reactants equal to the number of atoms in the products for I, K and Hg: I: | c_1 + 2 c_2 = 4 c_3 K: | c_1 = 2 c_3 Hg: | 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 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 KI + HgI_2 ⟶ K_2HgI_4

+ ⟶

potassium iodide + mercury(II) iodide ⟶ mercury potassium iodide

Construct the equilibrium constant, K, expression for: KI + HgI_2 ⟶ K_2HgI_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 KI + HgI_2 ⟶ K_2HgI_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 KI | 2 | -2 HgI_2 | 1 | -1 K_2HgI_4 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression KI | 2 | -2 | ([KI])^(-2) HgI_2 | 1 | -1 | ([HgI2])^(-1) K_2HgI_4 | 1 | 1 | [K2HgI4] 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 = ([KI])^(-2) ([HgI2])^(-1) [K2HgI4] = ([K2HgI4])/(([KI])^2 [HgI2])

Construct the rate of reaction expression for: KI + HgI_2 ⟶ K_2HgI_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 KI + HgI_2 ⟶ K_2HgI_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 KI | 2 | -2 HgI_2 | 1 | -1 K_2HgI_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 KI | 2 | -2 | -1/2 (Δ[KI])/(Δt) HgI_2 | 1 | -1 | -(Δ[HgI2])/(Δt) K_2HgI_4 | 1 | 1 | (Δ[K2HgI4])/(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[KI])/(Δt) = -(Δ[HgI2])/(Δt) = (Δ[K2HgI4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| potassium iodide | mercury(II) iodide | mercury potassium iodide formula | KI | HgI_2 | K_2HgI_4 Hill formula | IK | HgI_2 | HgI_4K_2 name | potassium iodide | mercury(II) iodide | mercury potassium iodide IUPAC name | potassium iodide | diiodomercury | dipotassium tetraiodomercury

| potassium iodide | mercury(II) iodide | mercury potassium iodide molar mass | 166.0028 g/mol | 454.401 g/mol | 786.406 g/mol phase | solid (at STP) | solid (at STP) | liquid (at STP) melting point | 681 °C | 259 °C | -38.9 °C boiling point | 1330 °C | 354 °C | 356.6 °C density | 3.123 g/cm^3 | 6.36 g/cm^3 | 1.097 g/cm^3 solubility in water | | insoluble | very soluble dynamic viscosity | 0.0010227 Pa s (at 732.9 °C) | 2.137×10^-5 Pa s (at 227 °C) | odor | | odorless |