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1. ************************************************************************************************************************************************ • Chemistry for Engineers • POP-up QUIZ : Thermodynamics • Name__________________ID___________NANO/ADME/AERO • ************************************************************************* good luck! Q1: Q3: For the following processes, decide (and explain) whether each is expected to be entropically favourable (DS = +ve) or unfavourable (DS = -ve) ? a) 2Sr(s) + O2 (g) 2SrO(s) b) FeCl3(s) Fe3+ (aq) + 3Cl- (aq) c) H2 (g) + I2(s) 2HI(g) negative (ordered salt forms from disordered gas) positive (ions in fixed salt lattice become mobile in solution) cmetal = 0.53 J/g·K positive (one mole of gas is converted into 2 moles of gas -disorder increases) (show working here, 6 marks) (6 marks) • Q2: From the following thermodynamic data: • 2C4H10(g)+ 13O2(g)8CO2(g) + 10H2O(l)DH = -5760 kJmol-1 • C(s) + O2(g)CO2(g)DH = -394 kJmol-1 • H2(g) + ½O2(g)H2O(l)DH = -286 kJmol-1 • a) What is the value of DHc(C4H10) , the molar heat of combustion • of butane? ____________________________________ • b) Use Hess’ Law to indirectly (from the equations above) calculate • the heat of formation of butane according to the equation: • 4C(s) + 5H2(g)C4H10(g)DH = ??? kJmol-1 • c) Is the formation of butane endothermic or exothermic? • ________________________ Q4: a) Given the following heat of formation and absolute entropy data, calculate DH and DS for the boiling of HCN b) Calculate the boiling point of HCN (the temperature when liquid and vapour are in equilibrum) 5760 / 2 = 2880 kJ/mol (2 marks) DHf (kJmol-1) S (JK-1mol-1) HCN (l) +109 113 HCN (g) +135 202 DHvapº (HCN) = +26 kJ/mol DSvapº (HCN) = +89 kJ/mol DHfº (C4H10) = -126 kJ/mol (7 marks) (3+ 5 marks) exothermic (1 marks) b.p. (HCN) = 292 K (19 ºC) Total: 30 marks