Unit 4 Part 2 Chem OR Exam

Which of the following statements is true about

q and w?

• 1. The sign of w is positive when work is done

  by the system

• 2. The sign of q is negative when work is done

  on the system

• 3. Work is a path function

• 4. Heat is a state function

Which of the following statements is/are true

concerning the first law of thermodynamics?

I) The internal energy (U) of the universe is

conserved

II) The internal energy of a system plus that

of its surroundings is conserved

III) The change in internal energy (ΔU) of a

system and its surrounding can have the

same sign

1. I, III

2. I only

3. I, II, III

4. III only

5. I, II

• 1.

• 2.

• 3.

• 4.

• 5.

ΔU = q + w

ΔSuniv

• ΔSuniv > 0 if a process is spontaneous

• ΔSuniv and ΔGsys are easily related

• ΔSsurr = – ΔHsys/T

• ΔSuniv = ΔSsys + ΔSsurr

• ΔSuniv < 0 if a process is spontaneous

When gases are formed

• ΔSsys is (+)

• ΔSsys is (-)

When Δn(gas) decrease

• ΔS is (-)

• ΔS is (+)

When Δn(total) increases

• ΔS is (-)

• ΔS is (+)

When Δn(gas) and Δn(tot) = 0

• ΔS ≈ 0

• ΔS is (+)

• ΔS is (-)

ΔSuniv

• ΔSsys + ΔSsurr

• – ΔHsys/T

ΔSsurr

• ΔSsys + ΔSsurr

• – ΔHsys/T