Can you calculate the amount of heat absorbed when carbon monoxide does 339J of work while expanding? The change in internal energy is -0.074KJ.

Im not sure if I did this correctly.

1 Answer
Truong-Son N.
Dec 12, 2017

Well, it's possible to do this, sure...

From the first law of thermodynamics,

#DeltaE = q + w#

#= q - PDeltaV#

for a thermodynamically-closed system. You were apparently given the work in #"J"# directly (normally you have to do the unit conversion yourself), and so, the only complication is the sign convention.

  • Work was done by the gas, so it must be negative with respect to the gas.
  • The change in internal energy is negative.
  • #|w| > |DeltaE|#, so #q > 0#.

Thus, we anticipate the heat to be absorbed.

#color(blue)(q) = DeltaE - w#

#= -"0.074 kJ" - (-339 xx 10^(-3) "kJ")#

#= color(blue)(+"0.265 kJ")# of heat flow

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