Chp 9 - Thermodynamics

Question 1

Energy can be converted from one form to another but can’t be created or destroyed.

Answer 1

• 1st law of thermodynamics

* Energy of system = –Energy of surroundings

Question 2

Difference between exothermic and endothermic?

Answer 2

• Exo- gives off heat (-)

* Endo- system accepts heat (+)

Question 3

In an energy level diagram, what is the layout?

Answer 3

• Unstable (top) to stable (bottom)
• Exo is downward arrow
• Endo is upward arrow
• Unstable tend to be multiple compound

Question 4

What is a better equation for energy of the system?

Answer 4

• ΔU = q + w

* w = –PΔV

Question 5

When are q and w positive and negative?

Answer 5

• w- done by system (–) done on system (+)

* q- heat absorbed by system (+) by surroundings (–)

Question 6

How many Joules are in L•atm?

Answer 6

101.3 J

Always do after -PΔV

Question 7

Heat absorbed/released Eq?

Answer 7

q = mCΔT

Question 8

Define open, closed, and isolated system?

Answer 8

• open- exchange of mass, energy
• closed- exchange of energy
• iso- nothing

Question 9

How to tell heat absorb of calorimeter?

Answer 9

• NET q = 0
• –q = q
• –mCΔT = mCΔT

Question 10

Formula for bomb calorimetry?

Answer 10

q = CΔT

Question 11

What is enthalpy Eq?

Answer 11

• H(products) – H(reactants)

* E-W

Question 12

Define the stoichiometry of Hess’s Law.

Answer 12

Whatever is done to Delta H must be done to chem Eq. Always set up proportions with kJ and mol