HCl + KCN = KCl + HCN

HCl hydrogen chloride + KCN potassium cyanide ⟶ KCl potassium chloride + HCN hydrogen cyanide

Balance the chemical equation algebraically: HCl + KCN ⟶ KCl + HCN Add stoichiometric coefficients, c_i, to the reactants and products: c_1 HCl + c_2 KCN ⟶ c_3 KCl + c_4 HCN Set the number of atoms in the reactants equal to the number of atoms in the products for Cl, H, C, K and N: Cl: | c_1 = c_3 H: | c_1 = c_4 C: | c_2 = c_4 K: | c_2 = c_3 N: | 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: | | HCl + KCN ⟶ KCl + HCN

+ ⟶ +

hydrogen chloride + potassium cyanide ⟶ potassium chloride + hydrogen cyanide

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

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

| hydrogen chloride | potassium cyanide | potassium chloride | hydrogen cyanide formula | HCl | KCN | KCl | HCN Hill formula | ClH | CKN | ClK | CHN name | hydrogen chloride | potassium cyanide | potassium chloride | hydrogen cyanide IUPAC name | hydrogen chloride | potassium cyanide | potassium chloride | formonitrile

| hydrogen chloride | potassium cyanide | potassium chloride | hydrogen cyanide molar mass | 36.46 g/mol | 65.116 g/mol | 74.55 g/mol | 27.026 g/mol phase | gas (at STP) | | solid (at STP) | liquid (at STP) melting point | -114.17 °C | | 770 °C | -13.4 °C boiling point | -85 °C | | 1420 °C | 25.6 °C density | 0.00149 g/cm^3 (at 25 °C) | | 1.98 g/cm^3 | 0.697 g/cm^3 solubility in water | miscible | | soluble | miscible surface tension | | | | 0.0172 N/m dynamic viscosity | | | | 1.83×10^-4 Pa s (at 25 °C) odor | | | odorless |