Chemistry 152 A Winter 2007 Quiz # 1 – Answer Key Possibly useful information: 1 atm = 101 KPascal; R = 8.2 J/oK/mol; PV = nRT; ΔΕ = Q + W; H = E + PV; W = - PexΔV; ΔΗ = Qp; 1 L atm = 101 J. 1) Energy and enthalpy, 6 points. A balloon, containing a fixed mass of a monoatomic ideal gas, is expanding its volume as heat is absorbed at an external pressure of 1 atm. Assume that ONLY “PV” work against the atmosphere is involved, in addition to the added heat. The balloon + the gas it contains is “the system.” Everything else is “the surroundings.” At the point where the volume of the balloon has increased by ΔV = 8L, answer the following if ΔEsysis then also measured to be 100 J: a)What is Wsys? Show work or state logic, get units and sign “right!” Wsys= - PΔV = - (1 atm) . (8 L) . 101 J/ atm L = - 808 JOr Wsys= - PΔV = - (1 atm . 101x10-3Pa/atm) . (8 L . 10-3m3/L) = - 808 J Wsys= - 808 J b)What is Qsurroundings
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