Mg + S8 = MgS

Mg magnesium + S_8 rhombic sulfur ⟶ MgS magnesium sulfide

Balance the chemical equation algebraically: Mg + S_8 ⟶ MgS Add stoichiometric coefficients, c_i, to the reactants and products: c_1 Mg + c_2 S_8 ⟶ c_3 MgS Set the number of atoms in the reactants equal to the number of atoms in the products for Mg and S: Mg: | c_1 = c_3 S: | 8 c_2 = c_3 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 = 8 c_2 = 1 c_3 = 8 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | 8 Mg + S_8 ⟶ 8 MgS

+ ⟶

magnesium + rhombic sulfur ⟶ magnesium sulfide

Construct the equilibrium constant, K, expression for: Mg + S_8 ⟶ MgS 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: 8 Mg + S_8 ⟶ 8 MgS 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 Mg | 8 | -8 S_8 | 1 | -1 MgS | 8 | 8 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression Mg | 8 | -8 | ([Mg])^(-8) S_8 | 1 | -1 | ([S8])^(-1) MgS | 8 | 8 | ([MgS])^8 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 = ([Mg])^(-8) ([S8])^(-1) ([MgS])^8 = ([MgS])^8/(([Mg])^8 [S8])

Construct the rate of reaction expression for: Mg + S_8 ⟶ MgS 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: 8 Mg + S_8 ⟶ 8 MgS 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 Mg | 8 | -8 S_8 | 1 | -1 MgS | 8 | 8 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 Mg | 8 | -8 | -1/8 (Δ[Mg])/(Δt) S_8 | 1 | -1 | -(Δ[S8])/(Δt) MgS | 8 | 8 | 1/8 (Δ[MgS])/(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 = -1/8 (Δ[Mg])/(Δt) = -(Δ[S8])/(Δt) = 1/8 (Δ[MgS])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| magnesium | rhombic sulfur | magnesium sulfide formula | Mg | S_8 | MgS name | magnesium | rhombic sulfur | magnesium sulfide IUPAC name | magnesium | octathiocane |

| magnesium | rhombic sulfur | magnesium sulfide molar mass | 24.305 g/mol | 256.5 g/mol | 56.36 g/mol phase | solid (at STP) | solid (at STP) | melting point | 648 °C | | 2226 °C boiling point | 1090 °C | | density | 1.738 g/cm^3 | 2.07 g/cm^3 | 2.68 g/cm^3 solubility in water | reacts | | reacts