CHEM 6B Lecture Notes - Lecture 4: Horse Length, Isolated System, Exothermic Process
6 Apr 2018
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Isolated system: has no contact with the surroundings. If w < 0 then expansion since work is done on the surroundings by the system. If w > 0 then compression since work is done on the system by the surroundings. If q > 0 then endothermic: 2h2 + o2 -> 2h2o (h2o is system) Is work done by the system on surroundings or on system by surroundings: w = -p v, w = - nrt, 3 moles becomes 2 moles, gas becomes liquid. 2 mol h2: a chemical reaction and enthalpy. Fe2o3 + 2al -> al2o3 + 2fe h = -851. 5 kj/mol exothermic like a product (that is produced). So2 -> s + o2 h = 298. 8 kj/mol endothermic like a reactant (that is needed) If -502. 6kj of heat was generated by the following reaction: 1 mol sncl2: under constant pressure, h = q, hess"s law: enthalpy changes for chemical equations are additive, given the following reactions:
