Oxygen dissolved in water can cause corrosion in hot-water heating systems. To remove oxygen, hydrazine (N₂H₄) is often added. Hydrazine reacts with dissolved O₂ to form water and N₂.
(a) Write a balanced chemical equation for the reaction of hydrazine and oxygen. Identify the oxidizing and reducing agents in this redox reaction.
(b) Calculate Δ_r H°, Δ_r S°, and Δ_rG° for this reaction involving 1 mol of N₂H₄ at 25°C.
(c) Because this is an exothermic reaction, energy is evolved as heat. What temperature change is expected in a heating system containing 5.5 × 10⁴ L of water? (Assume no energy is lost to the surroundings.)
(d) The mass of a hot-water heating system is 5.5 × 10⁴ kg. What amount of O₂ (in moles) would be present in this system if it is filled with water saturated with O₂? (The solubility of O₂ in water at 25°C is 0.000434 g per 100 g of water.)
(e) Assume hydrazine is available as a 5.0% solution in water. What mass of this solution should be added to totally consume the dissolved O₂ [described in part (d)]?
(f) Assuming the N₂ escapes as a gas, calculate the volume of N₂(g) (measured at 273 K and 1.00 atm) that will be produced.