H2SO4 + KNO2 + KCr2O7 = H2O + K2SO4 + Cr2(SO4)3 + KNO3

H_2SO_4 sulfuric acid + KNO_2 potassium nitrite + KCr2O7 ⟶ H_2O water + K_2SO_4 potassium sulfate + Cr_2(SO_4)_3 chromium sulfate + KNO_3 potassium nitrate

Balance the chemical equation algebraically: H_2SO_4 + KNO_2 + KCr2O7 ⟶ H_2O + K_2SO_4 + Cr_2(SO_4)_3 + KNO_3 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2SO_4 + c_2 KNO_2 + c_3 KCr2O7 ⟶ c_4 H_2O + c_5 K_2SO_4 + c_6 Cr_2(SO_4)_3 + c_7 KNO_3 Set the number of atoms in the reactants equal to the number of atoms in the products for H, O, S, K, N and Cr: H: | 2 c_1 = 2 c_4 O: | 4 c_1 + 2 c_2 + 7 c_3 = c_4 + 4 c_5 + 12 c_6 + 3 c_7 S: | c_1 = c_5 + 3 c_6 K: | c_2 + c_3 = 2 c_5 + c_7 N: | c_2 = c_7 Cr: | 2 c_3 = 2 c_6 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 = 7 c_2 = 7 c_3 = 2 c_4 = 7 c_5 = 1 c_6 = 2 c_7 = 7 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 7 H_2SO_4 + 7 KNO_2 + 2 KCr2O7 ⟶ 7 H_2O + K_2SO_4 + 2 Cr_2(SO_4)_3 + 7 KNO_3

+ + KCr2O7 ⟶ + + +

sulfuric acid + potassium nitrite + KCr2O7 ⟶ water + potassium sulfate + chromium sulfate + potassium nitrate

Construct the equilibrium constant, K, expression for: H_2SO_4 + KNO_2 + KCr2O7 ⟶ H_2O + K_2SO_4 + Cr_2(SO_4)_3 + KNO_3 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: 7 H_2SO_4 + 7 KNO_2 + 2 KCr2O7 ⟶ 7 H_2O + K_2SO_4 + 2 Cr_2(SO_4)_3 + 7 KNO_3 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 | 7 | -7 KNO_2 | 7 | -7 KCr2O7 | 2 | -2 H_2O | 7 | 7 K_2SO_4 | 1 | 1 Cr_2(SO_4)_3 | 2 | 2 KNO_3 | 7 | 7 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression H_2SO_4 | 7 | -7 | ([H2SO4])^(-7) KNO_2 | 7 | -7 | ([KNO2])^(-7) KCr2O7 | 2 | -2 | ([KCr2O7])^(-2) H_2O | 7 | 7 | ([H2O])^7 K_2SO_4 | 1 | 1 | [K2SO4] Cr_2(SO_4)_3 | 2 | 2 | ([Cr2(SO4)3])^2 KNO_3 | 7 | 7 | ([KNO3])^7 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])^(-7) ([KNO2])^(-7) ([KCr2O7])^(-2) ([H2O])^7 [K2SO4] ([Cr2(SO4)3])^2 ([KNO3])^7 = (([H2O])^7 [K2SO4] ([Cr2(SO4)3])^2 ([KNO3])^7)/(([H2SO4])^7 ([KNO2])^7 ([KCr2O7])^2)

Construct the rate of reaction expression for: H_2SO_4 + KNO_2 + KCr2O7 ⟶ H_2O + K_2SO_4 + Cr_2(SO_4)_3 + KNO_3 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: 7 H_2SO_4 + 7 KNO_2 + 2 KCr2O7 ⟶ 7 H_2O + K_2SO_4 + 2 Cr_2(SO_4)_3 + 7 KNO_3 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 | 7 | -7 KNO_2 | 7 | -7 KCr2O7 | 2 | -2 H_2O | 7 | 7 K_2SO_4 | 1 | 1 Cr_2(SO_4)_3 | 2 | 2 KNO_3 | 7 | 7 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 | 7 | -7 | -1/7 (Δ[H2SO4])/(Δt) KNO_2 | 7 | -7 | -1/7 (Δ[KNO2])/(Δt) KCr2O7 | 2 | -2 | -1/2 (Δ[KCr2O7])/(Δt) H_2O | 7 | 7 | 1/7 (Δ[H2O])/(Δt) K_2SO_4 | 1 | 1 | (Δ[K2SO4])/(Δt) Cr_2(SO_4)_3 | 2 | 2 | 1/2 (Δ[Cr2(SO4)3])/(Δt) KNO_3 | 7 | 7 | 1/7 (Δ[KNO3])/(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 = -1/7 (Δ[H2SO4])/(Δt) = -1/7 (Δ[KNO2])/(Δt) = -1/2 (Δ[KCr2O7])/(Δt) = 1/7 (Δ[H2O])/(Δt) = (Δ[K2SO4])/(Δt) = 1/2 (Δ[Cr2(SO4)3])/(Δt) = 1/7 (Δ[KNO3])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| sulfuric acid | potassium nitrite | KCr2O7 | water | potassium sulfate | chromium sulfate | potassium nitrate formula | H_2SO_4 | KNO_2 | KCr2O7 | H_2O | K_2SO_4 | Cr_2(SO_4)_3 | KNO_3 Hill formula | H_2O_4S | KNO_2 | Cr2KO7 | H_2O | K_2O_4S | Cr_2O_12S_3 | KNO_3 name | sulfuric acid | potassium nitrite | | water | potassium sulfate | chromium sulfate | potassium nitrate IUPAC name | sulfuric acid | potassium nitrite | | water | dipotassium sulfate | chromium(+3) cation trisulfate | potassium nitrate

| sulfuric acid | potassium nitrite | KCr2O7 | water | potassium sulfate | chromium sulfate | potassium nitrate molar mass | 98.07 g/mol | 85.103 g/mol | 255.08 g/mol | 18.015 g/mol | 174.25 g/mol | 392.2 g/mol | 101.1 g/mol phase | liquid (at STP) | solid (at STP) | | liquid (at STP) | | liquid (at STP) | solid (at STP) melting point | 10.371 °C | 350 °C | | 0 °C | | | 334 °C boiling point | 279.6 °C | | | 99.9839 °C | | 330 °C | density | 1.8305 g/cm^3 | 1.915 g/cm^3 | | 1 g/cm^3 | | 1.84 g/cm^3 | solubility in water | very soluble | | | | soluble | | soluble surface tension | 0.0735 N/m | | | 0.0728 N/m | | | dynamic viscosity | 0.021 Pa s (at 25 °C) | | | 8.9×10^-4 Pa s (at 25 °C) | | | odor | odorless | | | odorless | | odorless | odorless