H2SO4 + KBr = H2O + K2SO4 + S + Br2

Input interpretation

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H_2SO_4 sulfuric acid + KBr potassium bromide ⟶ H_2O water + K_2SO_4 potassium sulfate + S mixed sulfur + Br_2 bromine

Balanced equation

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Balance the chemical equation algebraically: H_2SO_4 + KBr ⟶ H_2O + K_2SO_4 + S + Br_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2SO_4 + c_2 KBr ⟶ c_3 H_2O + c_4 K_2SO_4 + c_5 S + c_6 Br_2 Set the number of atoms in the reactants equal to the number of atoms in the products for H, O, S, Br and K: H: | 2 c_1 = 2 c_3 O: | 4 c_1 = c_3 + 4 c_4 S: | c_1 = c_4 + c_5 Br: | c_2 = 2 c_6 K: | 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 = 4 c_2 = 6 c_3 = 4 c_4 = 3 c_5 = 1 c_6 = 3 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 4 H_2SO_4 + 6 KBr ⟶ 4 H_2O + 3 K_2SO_4 + S + 3 Br_2

+ ⟶ + + +

Names

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sulfuric acid + potassium bromide ⟶ water + potassium sulfate + mixed sulfur + bromine

Equilibrium constant

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Construct the equilibrium constant, K, expression for: H_2SO_4 + KBr ⟶ H_2O + K_2SO_4 + S + Br_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: 4 H_2SO_4 + 6 KBr ⟶ 4 H_2O + 3 K_2SO_4 + S + 3 Br_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 H_2SO_4 | 4 | -4 KBr | 6 | -6 H_2O | 4 | 4 K_2SO_4 | 3 | 3 S | 1 | 1 Br_2 | 3 | 3 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression H_2SO_4 | 4 | -4 | ([H2SO4])^(-4) KBr | 6 | -6 | ([KBr])^(-6) H_2O | 4 | 4 | ([H2O])^4 K_2SO_4 | 3 | 3 | ([K2SO4])^3 S | 1 | 1 | [S] Br_2 | 3 | 3 | ([Br2])^3 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])^(-4) ([KBr])^(-6) ([H2O])^4 ([K2SO4])^3 [S] ([Br2])^3 = (([H2O])^4 ([K2SO4])^3 [S] ([Br2])^3)/(([H2SO4])^4 ([KBr])^6)

Rate of reaction

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Construct the rate of reaction expression for: H_2SO_4 + KBr ⟶ H_2O + K_2SO_4 + S + Br_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: 4 H_2SO_4 + 6 KBr ⟶ 4 H_2O + 3 K_2SO_4 + S + 3 Br_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 H_2SO_4 | 4 | -4 KBr | 6 | -6 H_2O | 4 | 4 K_2SO_4 | 3 | 3 S | 1 | 1 Br_2 | 3 | 3 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 | 4 | -4 | -1/4 (Δ[H2SO4])/(Δt) KBr | 6 | -6 | -1/6 (Δ[KBr])/(Δt) H_2O | 4 | 4 | 1/4 (Δ[H2O])/(Δt) K_2SO_4 | 3 | 3 | 1/3 (Δ[K2SO4])/(Δt) S | 1 | 1 | (Δ[S])/(Δt) Br_2 | 3 | 3 | 1/3 (Δ[Br2])/(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 = -1/4 (Δ[H2SO4])/(Δt) = -1/6 (Δ[KBr])/(Δt) = 1/4 (Δ[H2O])/(Δt) = 1/3 (Δ[K2SO4])/(Δt) = (Δ[S])/(Δt) = 1/3 (Δ[Br2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)