CHEM 2045C: Quiz 6 (10/19/07) NAME ________KEY_____________ N #_____________ Show your work for full credit Eng Q8059x06b 1. (2 pts) The heat content of a substance at constant pressure is called ENTHALPY and is given the symbol H (or Δ H) . 2. (1 pt) Which of the following are state functions? I. the volume of a balloon II. enthalpy III. the temperature of water in a coffee cup [a] I only [b] II only [c] III only [d] two of these [e] all of these [f] none of these 3. (2 pts) When is the change in enthalpy equal to the change in internal energy? When Δ V = 0. Recall Δ H = Δ E - P Δ V so Δ H = Δ E when Δ V = 0 . 4. (3 pts) A system absorbs 85 kJ of heat from its surroundings while doing 29 kJ of work on the surroundings. Calculate the change in internal energy of the system and determine whether the process is endothermic or exothermic. (problem 5.25a) q = +85 kJ absorbed from surroundings w = -29 kJ work is done onto the surroundings Δ E = q + w = 85 – 29 kJ = +56 kJ + means enthothermic
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