Na2S + NiCl2 = NaCl + NiS

Na_2S sodium sulfide + NiCl_2 nickel(II) chloride ⟶ NaCl sodium chloride + SNi nickel(II) sulfide

Balance the chemical equation algebraically: Na_2S + NiCl_2 ⟶ NaCl + SNi Add stoichiometric coefficients, c_i, to the reactants and products: c_1 Na_2S + c_2 NiCl_2 ⟶ c_3 NaCl + c_4 SNi Set the number of atoms in the reactants equal to the number of atoms in the products for Na, S, Cl and Ni: Na: | 2 c_1 = c_3 S: | c_1 = c_4 Cl: | 2 c_2 = c_3 Ni: | 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 = 2 c_4 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | Na_2S + NiCl_2 ⟶ 2 NaCl + SNi

+ ⟶ +

sodium sulfide + nickel(II) chloride ⟶ sodium chloride + nickel(II) sulfide

Construct the equilibrium constant, K, expression for: Na_2S + NiCl_2 ⟶ NaCl + SNi 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: Na_2S + NiCl_2 ⟶ 2 NaCl + SNi 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 Na_2S | 1 | -1 NiCl_2 | 1 | -1 NaCl | 2 | 2 SNi | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression Na_2S | 1 | -1 | ([Na2S])^(-1) NiCl_2 | 1 | -1 | ([NiCl2])^(-1) NaCl | 2 | 2 | ([NaCl])^2 SNi | 1 | 1 | [S1Ni1] 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 = ([Na2S])^(-1) ([NiCl2])^(-1) ([NaCl])^2 [S1Ni1] = (([NaCl])^2 [S1Ni1])/([Na2S] [NiCl2])

Construct the rate of reaction expression for: Na_2S + NiCl_2 ⟶ NaCl + SNi 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: Na_2S + NiCl_2 ⟶ 2 NaCl + SNi 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 Na_2S | 1 | -1 NiCl_2 | 1 | -1 NaCl | 2 | 2 SNi | 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 Na_2S | 1 | -1 | -(Δ[Na2S])/(Δt) NiCl_2 | 1 | -1 | -(Δ[NiCl2])/(Δt) NaCl | 2 | 2 | 1/2 (Δ[NaCl])/(Δt) SNi | 1 | 1 | (Δ[S1Ni1])/(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[Na2S])/(Δt) = -(Δ[NiCl2])/(Δt) = 1/2 (Δ[NaCl])/(Δt) = (Δ[S1Ni1])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| sodium sulfide | nickel(II) chloride | sodium chloride | nickel(II) sulfide formula | Na_2S | NiCl_2 | NaCl | SNi Hill formula | Na_2S_1 | Cl_2Ni | ClNa | NiS name | sodium sulfide | nickel(II) chloride | sodium chloride | nickel(II) sulfide IUPAC name | | dichloronickel | sodium chloride | sulfanylidenenickel

| sodium sulfide | nickel(II) chloride | sodium chloride | nickel(II) sulfide molar mass | 78.04 g/mol | 129.6 g/mol | 58.44 g/mol | 90.75 g/mol phase | solid (at STP) | | solid (at STP) | melting point | 1172 °C | | 801 °C | boiling point | | | 1413 °C | density | 1.856 g/cm^3 | 3.55 g/cm^3 | 2.16 g/cm^3 | solubility in water | | | soluble | odor | | | odorless |