I2 + Hg = HgI2

I_2 iodine + Hg mercury ⟶ HgI_2 mercury(II) iodide

Balance the chemical equation algebraically: I_2 + Hg ⟶ HgI_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 I_2 + c_2 Hg ⟶ c_3 HgI_2 Set the number of atoms in the reactants equal to the number of atoms in the products for I and Hg: I: | 2 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_1 = 1 and solve the system of equations for the remaining coefficients: c_1 = 1 c_2 = 1 c_3 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | I_2 + Hg ⟶ HgI_2

+ ⟶

iodine + mercury ⟶ mercury(II) iodide

Construct the equilibrium constant, K, expression for: I_2 + Hg ⟶ HgI_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: I_2 + Hg ⟶ HgI_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 I_2 | 1 | -1 Hg | 1 | -1 HgI_2 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression I_2 | 1 | -1 | ([I2])^(-1) Hg | 1 | -1 | ([Hg])^(-1) HgI_2 | 1 | 1 | [HgI2] 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 = ([I2])^(-1) ([Hg])^(-1) [HgI2] = ([HgI2])/([I2] [Hg])

Construct the rate of reaction expression for: I_2 + Hg ⟶ HgI_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: I_2 + Hg ⟶ HgI_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 I_2 | 1 | -1 Hg | 1 | -1 HgI_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 I_2 | 1 | -1 | -(Δ[I2])/(Δt) Hg | 1 | -1 | -(Δ[Hg])/(Δt) HgI_2 | 1 | 1 | (Δ[HgI2])/(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[I2])/(Δt) = -(Δ[Hg])/(Δt) = (Δ[HgI2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| iodine | mercury | mercury(II) iodide formula | I_2 | Hg | HgI_2 name | iodine | mercury | mercury(II) iodide IUPAC name | molecular iodine | mercury | diiodomercury

| iodine | mercury | mercury(II) iodide molar mass | 253.80894 g/mol | 200.592 g/mol | 454.401 g/mol phase | solid (at STP) | liquid (at STP) | solid (at STP) melting point | 113 °C | -38.87 °C | 259 °C boiling point | 184 °C | 356.6 °C | 354 °C density | 4.94 g/cm^3 | 13.534 g/cm^3 | 6.36 g/cm^3 solubility in water | | slightly soluble | insoluble surface tension | | 0.47 N/m | dynamic viscosity | 0.00227 Pa s (at 116 °C) | 0.001526 Pa s (at 25 °C) | 2.137×10^-5 Pa s (at 227 °C) odor | | odorless | odorless