K + HClO4 = H2 + KClO4

K potassium + HClO_4 perchloric acid ⟶ H_2 hydrogen + KClO_4 potassium perchlorate

Balance the chemical equation algebraically: K + HClO_4 ⟶ H_2 + KClO_4 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 K + c_2 HClO_4 ⟶ c_3 H_2 + c_4 KClO_4 Set the number of atoms in the reactants equal to the number of atoms in the products for K, Cl, H and O: K: | c_1 = c_4 Cl: | c_2 = c_4 H: | c_2 = 2 c_3 O: | 4 c_2 = 4 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_3 = 1 and solve the system of equations for the remaining coefficients: c_1 = 2 c_2 = 2 c_3 = 1 c_4 = 2 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 K + 2 HClO_4 ⟶ H_2 + 2 KClO_4

+ ⟶ +

potassium + perchloric acid ⟶ hydrogen + potassium perchlorate

Construct the equilibrium constant, K, expression for: K + HClO_4 ⟶ H_2 + KClO_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: 2 K + 2 HClO_4 ⟶ H_2 + 2 KClO_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 K | 2 | -2 HClO_4 | 2 | -2 H_2 | 1 | 1 KClO_4 | 2 | 2 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression K | 2 | -2 | ([K])^(-2) HClO_4 | 2 | -2 | ([HClO4])^(-2) H_2 | 1 | 1 | [H2] KClO_4 | 2 | 2 | ([KClO4])^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 = ([K])^(-2) ([HClO4])^(-2) [H2] ([KClO4])^2 = ([H2] ([KClO4])^2)/(([K])^2 ([HClO4])^2)

Construct the rate of reaction expression for: K + HClO_4 ⟶ H_2 + KClO_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: 2 K + 2 HClO_4 ⟶ H_2 + 2 KClO_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 K | 2 | -2 HClO_4 | 2 | -2 H_2 | 1 | 1 KClO_4 | 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 K | 2 | -2 | -1/2 (Δ[K])/(Δt) HClO_4 | 2 | -2 | -1/2 (Δ[HClO4])/(Δt) H_2 | 1 | 1 | (Δ[H2])/(Δt) KClO_4 | 2 | 2 | 1/2 (Δ[KClO4])/(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 = -1/2 (Δ[K])/(Δt) = -1/2 (Δ[HClO4])/(Δt) = (Δ[H2])/(Δt) = 1/2 (Δ[KClO4])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| potassium | perchloric acid | hydrogen | potassium perchlorate formula | K | HClO_4 | H_2 | KClO_4 Hill formula | K | ClHO_4 | H_2 | ClKO_4 name | potassium | perchloric acid | hydrogen | potassium perchlorate IUPAC name | potassium | perchloric acid | molecular hydrogen | potassium perchlorate

| potassium | perchloric acid | hydrogen | potassium perchlorate molar mass | 39.0983 g/mol | 100.5 g/mol | 2.016 g/mol | 138.54 g/mol phase | solid (at STP) | liquid (at STP) | gas (at STP) | solid (at STP) melting point | 64 °C | -112 °C | -259.2 °C | 400 °C boiling point | 760 °C | 90 °C | -252.8 °C | density | 0.86 g/cm^3 | 1.77 g/cm^3 | 8.99×10^-5 g/cm^3 (at 0 °C) | 2.5239 g/cm^3 solubility in water | reacts | very soluble | | dynamic viscosity | | 8×10^-4 Pa s (at 25 °C) | 8.9×10^-6 Pa s (at 25 °C) | odor | | odorless | odorless |