KOH + Zn = K + Zn(OH)2

KOH potassium hydroxide + Zn zinc ⟶ K potassium + Zn(OH)_2 zinc hydroxide

Balance the chemical equation algebraically: KOH + Zn ⟶ K + Zn(OH)_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 KOH + c_2 Zn ⟶ c_3 K + c_4 Zn(OH)_2 Set the number of atoms in the reactants equal to the number of atoms in the products for H, K, O and Zn: H: | c_1 = 2 c_4 K: | c_1 = c_3 O: | c_1 = 2 c_4 Zn: | 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_2 = 1 and solve the system of equations for the remaining coefficients: c_1 = 2 c_2 = 1 c_3 = 2 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 2 KOH + Zn ⟶ 2 K + Zn(OH)_2

+ ⟶ +

potassium hydroxide + zinc ⟶ potassium + zinc hydroxide

Construct the equilibrium constant, K, expression for: KOH + Zn ⟶ K + Zn(OH)_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: 2 KOH + Zn ⟶ 2 K + Zn(OH)_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 KOH | 2 | -2 Zn | 1 | -1 K | 2 | 2 Zn(OH)_2 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression KOH | 2 | -2 | ([KOH])^(-2) Zn | 1 | -1 | ([Zn])^(-1) K | 2 | 2 | ([K])^2 Zn(OH)_2 | 1 | 1 | [Zn(OH)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 = ([KOH])^(-2) ([Zn])^(-1) ([K])^2 [Zn(OH)2] = (([K])^2 [Zn(OH)2])/(([KOH])^2 [Zn])

Construct the rate of reaction expression for: KOH + Zn ⟶ K + Zn(OH)_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: 2 KOH + Zn ⟶ 2 K + Zn(OH)_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 KOH | 2 | -2 Zn | 1 | -1 K | 2 | 2 Zn(OH)_2 | 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 KOH | 2 | -2 | -1/2 (Δ[KOH])/(Δt) Zn | 1 | -1 | -(Δ[Zn])/(Δt) K | 2 | 2 | 1/2 (Δ[K])/(Δt) Zn(OH)_2 | 1 | 1 | (Δ[Zn(OH)2])/(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[KOH])/(Δt) = -(Δ[Zn])/(Δt) = 1/2 (Δ[K])/(Δt) = (Δ[Zn(OH)2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| potassium hydroxide | zinc | potassium | zinc hydroxide formula | KOH | Zn | K | Zn(OH)_2 Hill formula | HKO | Zn | K | H_2O_2Zn name | potassium hydroxide | zinc | potassium | zinc hydroxide IUPAC name | potassium hydroxide | zinc | potassium | zinc dihydroxide

| potassium hydroxide | zinc | potassium | zinc hydroxide molar mass | 56.105 g/mol | 65.38 g/mol | 39.0983 g/mol | 99.39 g/mol phase | solid (at STP) | solid (at STP) | solid (at STP) | melting point | 406 °C | 420 °C | 64 °C | boiling point | 1327 °C | 907 °C | 760 °C | density | 2.044 g/cm^3 | 7.14 g/cm^3 | 0.86 g/cm^3 | solubility in water | soluble | insoluble | reacts | dynamic viscosity | 0.001 Pa s (at 550 °C) | | | odor | | odorless | |