K + MgBr = Mg + KBr

K potassium + MgBr ⟶ Mg magnesium + KBr potassium bromide

Balance the chemical equation algebraically: K + MgBr ⟶ Mg + KBr Add stoichiometric coefficients, c_i, to the reactants and products: c_1 K + c_2 MgBr ⟶ c_3 Mg + c_4 KBr Set the number of atoms in the reactants equal to the number of atoms in the products for K, Mg and Br: K: | c_1 = c_4 Mg: | c_2 = c_3 Br: | 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: | | K + MgBr ⟶ Mg + KBr

+ MgBr ⟶ +

potassium + MgBr ⟶ magnesium + potassium bromide

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

Construct the rate of reaction expression for: K + MgBr ⟶ Mg + KBr 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: K + MgBr ⟶ Mg + KBr 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 | 1 | -1 MgBr | 1 | -1 Mg | 1 | 1 KBr | 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 K | 1 | -1 | -(Δ[K])/(Δt) MgBr | 1 | -1 | -(Δ[MgBr])/(Δt) Mg | 1 | 1 | (Δ[Mg])/(Δt) KBr | 1 | 1 | (Δ[KBr])/(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[K])/(Δt) = -(Δ[MgBr])/(Δt) = (Δ[Mg])/(Δt) = (Δ[KBr])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| potassium | MgBr | magnesium | potassium bromide formula | K | MgBr | Mg | KBr Hill formula | K | BrMg | Mg | BrK name | potassium | | magnesium | potassium bromide

| potassium | MgBr | magnesium | potassium bromide molar mass | 39.0983 g/mol | 104.21 g/mol | 24.305 g/mol | 119 g/mol phase | solid (at STP) | | solid (at STP) | solid (at STP) melting point | 64 °C | | 648 °C | 734 °C boiling point | 760 °C | | 1090 °C | 1435 °C density | 0.86 g/cm^3 | | 1.738 g/cm^3 | 2.75 g/cm^3 solubility in water | reacts | | reacts | soluble