Problem 2Bridge between Denmark and Sweden. The combined tunnel and bridge between Copenhagen and Malmö uses concrete and steel; this problem concerns reactions in their production and degradation. Concrete is made from cement, water, sand and stones. Cement consists mainly of calcium silicates and aluminates; in the final step some gypsum, CaSOX4⋅2HX2O, is added to improve hardening. Elevated temperatures may form unwanted hemihydrate: CaSOX4⋅2HX2O(s)CaSOX4⋅21HX2O(s)+23HX2O(g). Thermodynamic data at 25∘C, 1.00 bar — CaSOX4⋅2HX2O(s): ΔHf∘=−2021.0 kJ mol−1, S∘=194.0 J K−1 mol−1; CaSOX4⋅21HX2O(s): −1575.0 kJ mol−1, 130.5 J K−1 mol−1; HX2O(g): −241.8 kJ mol−1, 188.6 J K−1 mol−1. R=8.314 J mol−1 K−1; 0∘C=273.15 K. (2.1) Calculate ΔH∘ for the transformation of 1.00 kg of CaSOX4⋅2HX2O(s) into hemihydrate; is it endothermic or exothermic? (2.2) Calculate the equilibrium water-vapour pressure (bar) in a closed vessel containing CaSOX4⋅2HX2O(s), CaSOX4⋅21HX2O(s) and HX2O(g) at 25∘C. (2.3) Calculate the temperature at which the equilibrium water-vapour pressure is 1.00 bar, assuming ΔH∘ and ΔS∘ are temperature-independent. Corrosion of iron involves the electrode reactions Fe(s)FeX2+(aq)+2eX− and OX2(g)+2HX2O(l)+4eX−4OHX−(aq). Consider the cell Fe(s)∣FeX2+(aq)∣∣OHX−(aq),OX2(g)∣Pt(s) at 25∘C with E∘(FeX2+/Fe)=−0.44 V and E∘(OX2/OHX−)=+0.40 V; RTln10/F=0.05916 V, F=96485 C mol−1. (2.4) Calculate the standard EMF at 25∘C. (2.5) Write the overall discharge reaction. (2.6) Calculate the equilibrium constant at 25∘C. (2.7) The cell runs 24 h at a constant 0.12 A under standard conditions; calculate the mass of Fe converted to FeX2+. (2.8) Calculate E for [FeX2+]=0.015 M, pH of the right half-cell 9.00, p(OX2)=0.700 bar.Solutions: 1