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SECTION B Answer all questions in this section. Question 1 (Soalan 1) (a) What makes substances undergo phase changes? in your explanation, use the solid-liquid transition between ice and liquid water as example. Apakah yang menyebabkan bahan-bahan melalul perubahan fasa. Dalam penerangan anda, gunakan peralihan pepejal-cecair of antara ais dan cecair air sebagai contoh. (4 marks) (b) The normal boiling point of liquid mercury. Hg (1); is 357C. The vapor pressure of liquid mercury at 250C is 75 forr. Caiculate the enthalpy of vaporization of mercury, in kJ/mol. Takat didih normal bagi cecair morkun, Hg(i), adalah 357C. Tekanan wap bagi cecair merkuni pada 250C adalah 75 forr Kirakan entalpi pengewapan merkuni dalam kJ/mol. (8 marks) Question 2 (Soalan 2) (a) State and justify the thermodynamic criterion for solution-vapour equilibrium. Nyata dan jelaskan kriteria termodinamik bagi keseimbangan larutan-wap. (3 marks) (b) Calculate the Gibbs energy, entropy and enthalpy of mixing when 1.0molC6H14 (hexane) is mixed with 1.00molC7H15 (heptane) at 25C : treat the solution as ideal. Kirakan tenaga Gibbs, entropi dan entalpi bagi pencampuran apabila 1.0molC6H14 (heksana) dicampurkan dengan 1.00mol CH16 (heptana) pada 25C; anggap larutan adalah ideal. (7 marks)