Na2S + Cd(NO3)2 = NaNO3 + CdS

Na_2S sodium sulfide + Cd(NO3)2 ⟶ NaNO_3 sodium nitrate + CdS cadmium sulfide

Balance the chemical equation algebraically: Na_2S + Cd(NO3)2 ⟶ NaNO_3 + CdS Add stoichiometric coefficients, c_i, to the reactants and products: c_1 Na_2S + c_2 Cd(NO3)2 ⟶ c_3 NaNO_3 + c_4 CdS Set the number of atoms in the reactants equal to the number of atoms in the products for Na, S, Cd, N and O: Na: | 2 c_1 = c_3 S: | c_1 = c_4 Cd: | c_2 = c_4 N: | 2 c_2 = c_3 O: | 6 c_2 = 3 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_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 + Cd(NO3)2 ⟶ 2 NaNO_3 + CdS

+ Cd(NO3)2 ⟶ +

sodium sulfide + Cd(NO3)2 ⟶ sodium nitrate + cadmium sulfide

Construct the equilibrium constant, K, expression for: Na_2S + Cd(NO3)2 ⟶ NaNO_3 + CdS 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 + Cd(NO3)2 ⟶ 2 NaNO_3 + CdS 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 Cd(NO3)2 | 1 | -1 NaNO_3 | 2 | 2 CdS | 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) Cd(NO3)2 | 1 | -1 | ([Cd(NO3)2])^(-1) NaNO_3 | 2 | 2 | ([NaNO3])^2 CdS | 1 | 1 | [CdS] 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) ([Cd(NO3)2])^(-1) ([NaNO3])^2 [CdS] = (([NaNO3])^2 [CdS])/([Na2S] [Cd(NO3)2])

Construct the rate of reaction expression for: Na_2S + Cd(NO3)2 ⟶ NaNO_3 + CdS 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 + Cd(NO3)2 ⟶ 2 NaNO_3 + CdS 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 Cd(NO3)2 | 1 | -1 NaNO_3 | 2 | 2 CdS | 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) Cd(NO3)2 | 1 | -1 | -(Δ[Cd(NO3)2])/(Δt) NaNO_3 | 2 | 2 | 1/2 (Δ[NaNO3])/(Δt) CdS | 1 | 1 | (Δ[CdS])/(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[Cd(NO3)2])/(Δt) = 1/2 (Δ[NaNO3])/(Δt) = (Δ[CdS])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| sodium sulfide | Cd(NO3)2 | sodium nitrate | cadmium sulfide formula | Na_2S | Cd(NO3)2 | NaNO_3 | CdS Hill formula | Na_2S_1 | CdN2O6 | NNaO_3 | CdS name | sodium sulfide | | sodium nitrate | cadmium sulfide IUPAC name | | | sodium nitrate | thioxocadmium

| sodium sulfide | Cd(NO3)2 | sodium nitrate | cadmium sulfide molar mass | 78.04 g/mol | 236.42 g/mol | 84.994 g/mol | 144.47 g/mol phase | solid (at STP) | | solid (at STP) | solid (at STP) melting point | 1172 °C | | 306 °C | 1400 °C density | 1.856 g/cm^3 | | 2.26 g/cm^3 | 4.82 g/cm^3 solubility in water | | | soluble | dynamic viscosity | | | 0.003 Pa s (at 250 °C) |