Thermochemistry is the study of heat and its relation to chemical reactions.

Things to remember:

• exothermic: a change that releases heat
  • i.e. combustion reactions
• endothermic: a change that absorbs heat
  • i.e. icy-hot (cold pack)
• enthalpy (H): sum of internal energy
• $\Delta H$: change of enthalpy
  • $\Delta H$ < 0: exothermic
  • $\Delta H$ > 0: endothermic
• $q = m c \Delta T$
  • • $q$: heat
    • $m$: mass
    • $c$: specific heat
    • $\Delta T$: change in temperature
• entropy (ΔS): quantitative measurement of disorder
  • $\Delta S$ < 0: decreasing disorder
  • $\Delta S$ > 0: increasing disorder
• $\Delta G$: favorability/spontaneity
  • $\Delta G$ < 0: FAVORABLE; spontaneous; the reaction releases energy; proceeds without the input of energy
  • $\Delta G$ > 0: NOT FAVORABLE; not spontaneous; requires energy to proceed
  • REMEMBER when looking at our definition of spontaneous google reads “performed or occurring as a result of a sudden inner impulse or inclination and without premeditation or external stimulus.” Do not think of this is as a random occurrence, but the favorability to happen without the input of energy

All this information will tie back to one of our equations:

$\Delta G = \Delta H – T\Delta S$

Try making a chart as to how all the different pieces of this equation connects based on the information above; write out the reasoning as to why it makes sense.

Reading and setting up the problem: