For the following processes, state whether each of the four thermodynamic quanti
ID: 1658308 • Letter: F
Question
For the following processes, state whether each of the four thermodynamic quantities q, u, U and H is greater than equal to or less than zero for the system described. Consider all gases to behave ideally. Part A Two copper bars, one initially at 80° C and the other initially at 20°C, are brought into contact with each other in a themally insulated compartment and then allowed to come to equilibrium. (Assume no volume change.) Submit My Answers Give Up Part B A sample of liquid in a thermally insulated container (a calorimeter) is stirred for 1 h by a mechanical linkage to a motor in the surroundings. (Assume that expansion of the system is negligible.) Submit My Answers Give UR Part C A sample of H2 gas is mixed with an equimolar amount of N2 gas at the same temperature and pressure under conditions where no chemical reaction occurs between them. (Assume ideal gas behaviour.) Submit My Answers Give UpExplanation / Answer
a) Two copper bars, one initially at 80 degrees celsius and the other initially at 20 degrees celsius, are brought into contact with each other in a thermally insulated compartment and then allowed to come to equilibrium.
In this case the system is insulated so there is no heat exchange between sysytem and surroundings. Therefore,
q = 0 then U = w according to first law of thermodynamics. and U = H
b) A sample of liquid in a thermally insulated container (a calorimeter) is stirred for 1 hour by a mechanical linkage to a motor in the surroundings.
In this case motor is working on system. then work done on the sytem w = +ve, q = +ve then U = +ve fromfirst law of thermodynamics. H = +ve ( since change in volume is constant)
c) A sample of H2 gas is mixed with an equimolar amount of N2 gas at the same temperature and pressure under conditions where no chemical reaction occurs between them.
here no change in internal energy since temperature is constannt. U = 0 then q = -w and H = U + nRT
since T = 0 then H = 0
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