H2SO4 + KCl = HCl + KHSO4

H_2SO_4 sulfuric acid + KCl potassium chloride ⟶ HCl hydrogen chloride + KHSO_4 potassium bisulfate

Balance the chemical equation algebraically: H_2SO_4 + KCl ⟶ HCl + KHSO_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 H_2SO_4 + c_2 KCl ⟶ c_3 HCl + c_4 KHSO_4 Set the number of atoms in the reactants equal to the number of atoms in the products for H, O, S, Cl and K: H: | 2 c_1 = c_3 + c_4 O: | 4 c_1 = 4 c_4 S: | c_1 = c_4 Cl: | c_2 = c_3 K: | c_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_1 = 1 and solve the system of equations for the remaining coefficients: c_1 = 1 c_2 = 1 c_3 = 1 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | H_2SO_4 + KCl ⟶ HCl + KHSO_4

+ ⟶ +

sulfuric acid + potassium chloride ⟶ hydrogen chloride + potassium bisulfate

| sulfuric acid | potassium chloride | hydrogen chloride | potassium bisulfate molecular enthalpy | -814 kJ/mol | -436.5 kJ/mol | -92.3 kJ/mol | -1161 kJ/mol total enthalpy | -814 kJ/mol | -436.5 kJ/mol | -92.3 kJ/mol | -1161 kJ/mol | H_initial = -1251 kJ/mol | | H_final = -1253 kJ/mol | ΔH_rxn^0 | -1253 kJ/mol - -1251 kJ/mol = -2.4 kJ/mol (exothermic) | | |

| sulfuric acid | potassium chloride | hydrogen chloride | potassium bisulfate molecular free energy | -690 kJ/mol | -408.5 kJ/mol | -95.3 kJ/mol | -1031 kJ/mol total free energy | -690 kJ/mol | -408.5 kJ/mol | -95.3 kJ/mol | -1031 kJ/mol | G_initial = -1099 kJ/mol | | G_final = -1127 kJ/mol | ΔG_rxn^0 | -1127 kJ/mol - -1099 kJ/mol = -28.1 kJ/mol (exergonic) | | |

Construct the equilibrium constant, K, expression for: H_2SO_4 + KCl ⟶ HCl + KHSO_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: H_2SO_4 + KCl ⟶ HCl + KHSO_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 | 1 | -1 KCl | 1 | -1 HCl | 1 | 1 KHSO_4 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression H_2SO_4 | 1 | -1 | ([H2SO4])^(-1) KCl | 1 | -1 | ([KCl])^(-1) HCl | 1 | 1 | [HCl] KHSO_4 | 1 | 1 | [KHSO4] 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])^(-1) ([KCl])^(-1) [HCl] [KHSO4] = ([HCl] [KHSO4])/([H2SO4] [KCl])

Construct the rate of reaction expression for: H_2SO_4 + KCl ⟶ HCl + KHSO_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: H_2SO_4 + KCl ⟶ HCl + KHSO_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 | 1 | -1 KCl | 1 | -1 HCl | 1 | 1 KHSO_4 | 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 H_2SO_4 | 1 | -1 | -(Δ[H2SO4])/(Δt) KCl | 1 | -1 | -(Δ[KCl])/(Δt) HCl | 1 | 1 | (Δ[HCl])/(Δt) KHSO_4 | 1 | 1 | (Δ[KHSO4])/(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[H2SO4])/(Δt) = -(Δ[KCl])/(Δt) = (Δ[HCl])/(Δt) = (Δ[KHSO4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| sulfuric acid | potassium chloride | hydrogen chloride | potassium bisulfate formula | H_2SO_4 | KCl | HCl | KHSO_4 Hill formula | H_2O_4S | ClK | ClH | HKO_4S name | sulfuric acid | potassium chloride | hydrogen chloride | potassium bisulfate IUPAC name | sulfuric acid | potassium chloride | hydrogen chloride | potassium hydrogen sulfate

| sulfuric acid | potassium chloride | hydrogen chloride | potassium bisulfate molar mass | 98.07 g/mol | 74.55 g/mol | 36.46 g/mol | 136.16 g/mol phase | liquid (at STP) | solid (at STP) | gas (at STP) | solid (at STP) melting point | 10.371 °C | 770 °C | -114.17 °C | 214 °C boiling point | 279.6 °C | 1420 °C | -85 °C | density | 1.8305 g/cm^3 | 1.98 g/cm^3 | 0.00149 g/cm^3 (at 25 °C) | 2.32 g/cm^3 solubility in water | very soluble | soluble | miscible | surface tension | 0.0735 N/m | | | dynamic viscosity | 0.021 Pa s (at 25 °C) | | | odor | odorless | odorless | |