chemistry: chapter 6 zumdhal 9th edition

q in

endothermic, positive q

q out

exothermic, negative q

work done on system by surroundings

contractive, positive w

work done by system on surroundings

expansive, negative w

heat

total energy of all particles

temperature

average speed of all particles

equilibria

heat content isn’t the same, but the temperature and heart flow is the same both ways

why is exothermic spontaneous?

in exothermic reactions, the products are more stable

exothermic reaction energy diagram

delta H is negative

endothermic reaction energy diagram

delta H is positive

if (w → 0)

delta E = q, proportional to delta T

if (q → 0)

delta E = w = F *d,* proportional to P \* delta V

melting and freezing

melting - expansion

freezing - contraction

Hfusion

boiling and condensation

boiling - expansion

condensation - contraction

Hvaporization

sublimination and deposition

sublimination - expansion

deposition - contraction

state property

a propertiy in which we only care about the initial and final state, not the pathway in which we got there

calorimetry

study of heat transfer using a calorimeter

specific heat

the amount of heat it takes to increase one gram of a substance by one degree celcius

delta H =

\-qwater

bomb calorimeter is used when

there is lots of gas and high temperatures

qrxn =

\-qcalorimeter = -Ccalorimeter \* delta T

qsystem

qbomb+qH2O

phase change diagram

when the graph goes up

q = m \* c \* delta T

when the phase change graph stays constant

w = m \* Hx (x can be fusion or vaporization, it depends)

thermochem rule #1

delta H is directly propertional to the amount of reactands or products

thermochem rule #2

delta T for a reaction is equal in magnitude but opposite sign to delta H in reverse

thermochem rule #3

hess’ law

Hf

delta H when one molecule of stable compound is formed

bond energies

delta H when one mole of bonds are broken in the gaseous state

breaking bonds

positive

forming bonds

negative

lattice energy

energy released when two gaseous ions react to form a solid product

Hsolution

ionization energy + sphere of hydration

increasing lattice energy

least to most exothermic