H2SO4 + CaI2 = H2O + I2 + H2S + CaSO4

Input interpretation

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H_2SO_4 sulfuric acid + CaI_2 calcium iodide ⟶ H_2O water + I_2 iodine + H_2S hydrogen sulfide + CaSO_4 calcium sulfate

Balanced equation

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Balance the chemical equation algebraically: H_2SO_4 + CaI_2 ⟶ H_2O + I_2 + H_2S + CaSO_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2SO_4 + c_2 CaI_2 ⟶ c_3 H_2O + c_4 I_2 + c_5 H_2S + c_6 CaSO_4 Set the number of atoms in the reactants equal to the number of atoms in the products for H, O, S, Ca and I: H: | 2 c_1 = 2 c_3 + 2 c_5 O: | 4 c_1 = c_3 + 4 c_6 S: | c_1 = c_5 + c_6 Ca: | c_2 = c_6 I: | 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_5 = 1 and solve the system of equations for the remaining coefficients: c_1 = 5 c_2 = 4 c_3 = 4 c_4 = 4 c_5 = 1 c_6 = 4 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 5 H_2SO_4 + 4 CaI_2 ⟶ 4 H_2O + 4 I_2 + H_2S + 4 CaSO_4

+ ⟶ + + +

Names

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sulfuric acid + calcium iodide ⟶ water + iodine + hydrogen sulfide + calcium sulfate

Equilibrium constant

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Construct the equilibrium constant, K, expression for: H_2SO_4 + CaI_2 ⟶ H_2O + I_2 + H_2S + CaSO_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: 5 H_2SO_4 + 4 CaI_2 ⟶ 4 H_2O + 4 I_2 + H_2S + 4 CaSO_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 H_2SO_4 | 5 | -5 CaI_2 | 4 | -4 H_2O | 4 | 4 I_2 | 4 | 4 H_2S | 1 | 1 CaSO_4 | 4 | 4 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression H_2SO_4 | 5 | -5 | ([H2SO4])^(-5) CaI_2 | 4 | -4 | ([CaI2])^(-4) H_2O | 4 | 4 | ([H2O])^4 I_2 | 4 | 4 | ([I2])^4 H_2S | 1 | 1 | [H2S] CaSO_4 | 4 | 4 | ([CaSO4])^4 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 = ([H2SO4])^(-5) ([CaI2])^(-4) ([H2O])^4 ([I2])^4 [H2S] ([CaSO4])^4 = (([H2O])^4 ([I2])^4 [H2S] ([CaSO4])^4)/(([H2SO4])^5 ([CaI2])^4)

Rate of reaction

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Construct the rate of reaction expression for: H_2SO_4 + CaI_2 ⟶ H_2O + I_2 + H_2S + CaSO_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: 5 H_2SO_4 + 4 CaI_2 ⟶ 4 H_2O + 4 I_2 + H_2S + 4 CaSO_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 H_2SO_4 | 5 | -5 CaI_2 | 4 | -4 H_2O | 4 | 4 I_2 | 4 | 4 H_2S | 1 | 1 CaSO_4 | 4 | 4 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 H_2SO_4 | 5 | -5 | -1/5 (Δ[H2SO4])/(Δt) CaI_2 | 4 | -4 | -1/4 (Δ[CaI2])/(Δt) H_2O | 4 | 4 | 1/4 (Δ[H2O])/(Δt) I_2 | 4 | 4 | 1/4 (Δ[I2])/(Δt) H_2S | 1 | 1 | (Δ[H2S])/(Δt) CaSO_4 | 4 | 4 | 1/4 (Δ[CaSO4])/(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 = -1/5 (Δ[H2SO4])/(Δt) = -1/4 (Δ[CaI2])/(Δt) = 1/4 (Δ[H2O])/(Δt) = 1/4 (Δ[I2])/(Δt) = (Δ[H2S])/(Δt) = 1/4 (Δ[CaSO4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)