Knock out the false energy claims

Exercise and reference answers

Questions

1. Question

   Three of these statements about spontaneity are false.

   Choices

   1. Item

      At fixed T and p spontaneity needs dG < 0

      Correct

      Yes

   2. Explanation

      dG = 0 is equilibrium, not a non spontaneous change.

      Item

      dG = 0 marks a non spontaneous change

   3. Explanation

      In an isolated system a spontaneous change raises total entropy.

      Item

      An isolated system needs dS below zero

   4. Explanation

      With dG above zero the reverse change is the spontaneous one.

      Item

      dG above zero makes the change go

2. Question

   Three of these statements about the first law are false.

   Choices

   1. Item

      Expansion into a vacuum does zero work

      Correct

      Yes

   2. Explanation

      With q = 0 an adiabatic step reduces to dU = W.

      Item

      An adiabatic step reduces to dU = q

   3. Explanation

      Heat and work depend on the path taken, not on the state.

      Item

      Heat and work are both state functions

   4. Explanation

      Enthalpy is a state function, which is why Hess's law holds.

      Item

      Enthalpy is a path function

Instructions

Tap away the three false lines in each set about spontaneity and the first law.

Explanation