Worksheet: The First Law of Thermodynamics

In this worksheet, we will practice defining the first law of thermodynamics, which states that the total energy of an isolated system is constant.

Q1:

What is the first law of thermodynamics?

  • AThe energy of a system always increases in any physical or chemical process.
  • BThe energy of the universe (encompassing the system and the surroundings) is always conserved in any physical or chemical process.
  • CThe entropy of a system always increases in any spontaneous process.
  • DThe energy of a system always decreases in any physical or chemical process.

Q2:

Consider a cyclic process in which a system performs a net amount of work on its surroundings (i.e., 𝑤<0net corresponding to the net work done by the system). Would this process be endothermic (𝑞>0)net, exothermic (𝑞<0)net, or adiabatic (𝑞=0)net with respect to the net heat (𝑞)net exchange between system and surroundings? And what would be the relationship between 𝑞net and 𝑤net?

  • AEndothermic, with |𝑞|>|𝑤|netnet
  • BAdiabatic, with 𝑞=0net and 𝑤<0net
  • CEndothermic, with 𝑞=𝑤netnet
  • DExothermic, with 𝑞=𝑤<0netnet

Q3:

What is the first law of thermodynamics?

  • AThe force necessary to move an object is equal to its mass multiplied by its acceleration.
  • BAn object will remain static or in motion unless acted on by an external force.
  • CThe change in internal energy of a system is equal to the heat energy supplied to the system minus the work done by the system.
  • DThe partial pressure of each component of a mixture of ideal gases is equal to its vapor pressure multiplied by its mole fraction.

Q4:

Which of the following statements is correct?

  • AFor a closed system, Δ𝑆 can never have a negative value.
  • BFor an adiabatic process in a closed system, Δ𝑆 must be zero.
  • CFor a reversible process in a closed system, Δ𝑆 must be zero.
  • DFor an adiabatic process in a closed system, Δ𝑆 cannot have a negative value.

Q5:

The density of ice, HO()2s, at 273 K is 0.915 kg/dm3, and that of liquid water is 0.99987 kg/dm3. How much thermodynamic work must be done to melt 1.00 mol of ice at 1.00 bar pressure?

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