Spontaneity
What are examples of outside intervention?
-rusting -freezing water -ball rolling down a hill
What factors affect spontaneity?
1. changes in enthalpy 2. changes in entropy
what are 3 ways to increase entropy
1. increase temperature 2. phase changes or dissolving 3. change number of moles & particles
Are reactions spontaneous in both directions?
No, if a reaction is spontaneous in one direction, it is NOT spontaneous in the other direction
What is a specific condition that can determine if a reaction is spontaneous?
Temperature
combustion reactions are both __ & __
combustion reactions are both exothermic and spontaneous
What combination of entropy and enthalpy make a reaction that is never spontaneous?
endothermic (+Delta H) decrease entropy (-Delta S)
to make a non-spontaneous reaction occur ____
energy must be included
not all ___ reactions are spontaneous
exothermic some endothermic reactions can be spontaneous as well (ex: salt in water, vaporization)
What combination of entropy and enthalpy make a reaction that is always spontaneous?
exothermic (-Delta H) increase entropy (+Delta S)
Spontaneous reactions tend to be __
exothermic (but not always)
Describe how changes in enthalpy affect spontaneity
exothermic reactions tend to be favorable endothermic reactions tend to be unfavorable
What are examples of exothermic and endothermic spontaneous reactions?
exothermic: combustion endothermic: phase change
describe how changes in entropy affect spontaneity
increase entropy tend to be favorable decrease entropy tend to be unfavorable
What do spontaneous reactions need to overcome?
need to overcome activation energy
What is spontaneous process
process that occurs under a specific set of conditions without any outside intervention
What is an irreversible reaction? What is an example?
reaction that cannot return to the original process without a permanent change to the surroundings ex: chemical changes (cooking an egg)
what is a reversible reaction? What is an example?
reaction where both the system and the surroundings can be restored to their original states by exactly reversing the process ex: physical changes (Popsicle to juice)
what is an example of a non-spontaneous reaction?
un-rusting, ball going up a hill
