Input interpretation
H_2SO_4 sulfuric acid + K_2Cr_2O_7 potassium dichromate + CH_3CH_2OH ethanol ⟶ H_2O water + CH_3CHO acetaldehyde + CrKO_8S_2 chrome potash alum
Balanced equation
Balance the chemical equation algebraically: H_2SO_4 + K_2Cr_2O_7 + CH_3CH_2OH ⟶ H_2O + CH_3CHO + CrKO_8S_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2SO_4 + c_2 K_2Cr_2O_7 + c_3 CH_3CH_2OH ⟶ c_4 H_2O + c_5 CH_3CHO + c_6 CrKO_8S_2 Set the number of atoms in the reactants equal to the number of atoms in the products for H, O, S, Cr, K and C: H: | 2 c_1 + 6 c_3 = 2 c_4 + 4 c_5 O: | 4 c_1 + 7 c_2 + c_3 = c_4 + c_5 + 8 c_6 S: | c_1 = 2 c_6 Cr: | 2 c_2 = c_6 K: | 2 c_2 = c_6 C: | 2 c_3 = 2 c_5 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 = 4 c_2 = 1 c_3 = 3 c_4 = 7 c_5 = 3 c_6 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 4 H_2SO_4 + K_2Cr_2O_7 + 3 CH_3CH_2OH ⟶ 7 H_2O + 3 CH_3CHO + 2 CrKO_8S_2
Structures
+ + ⟶ + +
Names
sulfuric acid + potassium dichromate + ethanol ⟶ water + acetaldehyde + chrome potash alum
Equilibrium constant
Construct the equilibrium constant, K, expression for: H_2SO_4 + K_2Cr_2O_7 + CH_3CH_2OH ⟶ H_2O + CH_3CHO + CrKO_8S_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 + K_2Cr_2O_7 + 3 CH_3CH_2OH ⟶ 7 H_2O + 3 CH_3CHO + 2 CrKO_8S_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 K_2Cr_2O_7 | 1 | -1 CH_3CH_2OH | 3 | -3 H_2O | 7 | 7 CH_3CHO | 3 | 3 CrKO_8S_2 | 2 | 2 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) K_2Cr_2O_7 | 1 | -1 | ([K2Cr2O7])^(-1) CH_3CH_2OH | 3 | -3 | ([CH3CH2OH])^(-3) H_2O | 7 | 7 | ([H2O])^7 CH_3CHO | 3 | 3 | ([CH3CHO])^3 CrKO_8S_2 | 2 | 2 | ([CrKO8S2])^2 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) ([K2Cr2O7])^(-1) ([CH3CH2OH])^(-3) ([H2O])^7 ([CH3CHO])^3 ([CrKO8S2])^2 = (([H2O])^7 ([CH3CHO])^3 ([CrKO8S2])^2)/(([H2SO4])^4 [K2Cr2O7] ([CH3CH2OH])^3)
Rate of reaction
Construct the rate of reaction expression for: H_2SO_4 + K_2Cr_2O_7 + CH_3CH_2OH ⟶ H_2O + CH_3CHO + CrKO_8S_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 + K_2Cr_2O_7 + 3 CH_3CH_2OH ⟶ 7 H_2O + 3 CH_3CHO + 2 CrKO_8S_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 K_2Cr_2O_7 | 1 | -1 CH_3CH_2OH | 3 | -3 H_2O | 7 | 7 CH_3CHO | 3 | 3 CrKO_8S_2 | 2 | 2 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) K_2Cr_2O_7 | 1 | -1 | -(Δ[K2Cr2O7])/(Δt) CH_3CH_2OH | 3 | -3 | -1/3 (Δ[CH3CH2OH])/(Δt) H_2O | 7 | 7 | 1/7 (Δ[H2O])/(Δt) CH_3CHO | 3 | 3 | 1/3 (Δ[CH3CHO])/(Δt) CrKO_8S_2 | 2 | 2 | 1/2 (Δ[CrKO8S2])/(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) = -(Δ[K2Cr2O7])/(Δt) = -1/3 (Δ[CH3CH2OH])/(Δt) = 1/7 (Δ[H2O])/(Δt) = 1/3 (Δ[CH3CHO])/(Δt) = 1/2 (Δ[CrKO8S2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)
Chemical names and formulas
| sulfuric acid | potassium dichromate | ethanol | water | acetaldehyde | chrome potash alum formula | H_2SO_4 | K_2Cr_2O_7 | CH_3CH_2OH | H_2O | CH_3CHO | CrKO_8S_2 Hill formula | H_2O_4S | Cr_2K_2O_7 | C_2H_6O | H_2O | C_2H_4O | CrKO_8S_2 name | sulfuric acid | potassium dichromate | ethanol | water | acetaldehyde | chrome potash alum IUPAC name | sulfuric acid | dipotassium oxido-(oxido-dioxochromio)oxy-dioxochromium | ethanol | water | acetaldehyde | potassium chromium(+3) cation disulfate