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 decreases in any physical or chemical process.
  • BThe energy of a system always increases in any physical or chemical process.
  • CThe entropy of a system always increases in any spontaneous process.
  • DThe energy of the universe (encompassing the system and the surroundings) is always conserved 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 < 0 n e t corresponding to the net work done by the system). Would this process be endothermic ( 𝑞 > 0 ) n e t , exothermic ( 𝑞 < 0 ) n e t , or adiabatic ( 𝑞 = 0 ) n e t with respect to the net heat ( 𝑞 ) n e t exchange between system and surroundings? And what would be the relationship between 𝑞 n e t and 𝑤 n e t ?

  • AExothermic, with 𝑞 = 𝑤 < 0 n e t n e t
  • BEndothermic, with | 𝑞 | > | 𝑤 | n e t n e t
  • CAdiabatic, with 𝑞 = 0 n e t and 𝑤 < 0 n e t
  • DEndothermic, with 𝑞 = 𝑤 n e t n e t

Q3:

What is the first law of thermodynamics?

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

Q4:

Which of the following statements is correct?

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

Q5:

The density of ice, H O ( ) 2 s , 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?

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy.