O2 + Pt = PtO2

O_2 oxygen + Pt platinum ⟶ PtO_2 platinum(IV) oxide

Balance the chemical equation algebraically: O_2 + Pt ⟶ PtO_2 Add stoichiometric coefficients, c_i, to the reactants and products: c_1 O_2 + c_2 Pt ⟶ c_3 PtO_2 Set the number of atoms in the reactants equal to the number of atoms in the products for O and Pt: O: | 2 c_1 = 2 c_3 Pt: | 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_1 = 1 and solve the system of equations for the remaining coefficients: c_1 = 1 c_2 = 1 c_3 = 1 Substitute the coefficients into the chemical reaction to obtain the balanced equation: Answer: | | O_2 + Pt ⟶ PtO_2

+ ⟶

oxygen + platinum ⟶ platinum(IV) oxide

Construct the equilibrium constant, K, expression for: O_2 + Pt ⟶ PtO_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: O_2 + Pt ⟶ PtO_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 O_2 | 1 | -1 Pt | 1 | -1 PtO_2 | 1 | 1 Assemble the activity expressions accounting for the state of matter and ν_i: chemical species | c_i | ν_i | activity expression O_2 | 1 | -1 | ([O2])^(-1) Pt | 1 | -1 | ([Pt])^(-1) PtO_2 | 1 | 1 | [PtO2] 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 = ([O2])^(-1) ([Pt])^(-1) [PtO2] = ([PtO2])/([O2] [Pt])

Construct the rate of reaction expression for: O_2 + Pt ⟶ PtO_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: O_2 + Pt ⟶ PtO_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 O_2 | 1 | -1 Pt | 1 | -1 PtO_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 O_2 | 1 | -1 | -(Δ[O2])/(Δt) Pt | 1 | -1 | -(Δ[Pt])/(Δt) PtO_2 | 1 | 1 | (Δ[PtO2])/(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[O2])/(Δt) = -(Δ[Pt])/(Δt) = (Δ[PtO2])/(Δt) (assuming constant volume and no accumulation of intermediates or side products)

| oxygen | platinum | platinum(IV) oxide formula | O_2 | Pt | PtO_2 Hill formula | O_2 | Pt | O_2Pt name | oxygen | platinum | platinum(IV) oxide IUPAC name | molecular oxygen | platinum | dioxoplatinum

| oxygen | platinum | platinum(IV) oxide molar mass | 31.998 g/mol | 195.084 g/mol | 227.082 g/mol phase | gas (at STP) | solid (at STP) | solid (at STP) melting point | -218 °C | 1772 °C | 450 °C boiling point | -183 °C | 3827 °C | density | 0.001429 g/cm^3 (at 0 °C) | 21.45 g/cm^3 | 11.8 g/cm^3 solubility in water | | insoluble | insoluble surface tension | 0.01347 N/m | | dynamic viscosity | 2.055×10^-5 Pa s (at 25 °C) | | odor | odorless | |