CH test 2
Terms
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- Network Covalent Bonds
-
C
ZnS
SiO2 - rank bond strengths by melting point
-
dispersion
dipoledipole
h-bonding
= weak
metallic
= weak ---> strong
ionic bonds
covalent bonds
= strong - rank solids by melting point
-
SOLID M.P.
molecular low
metal low ---> high
ionic high
covalent high - Dalton's Atomic Theory - Part III
- in a reaction, atoms don't change, they rearrange
- First Law of Thermodynamics
-
ΔEuniv = 0
conservation of energy - To find the change in energy of a system:
- ΔEsys = q + w
- enthalpy
-
H
ΔH - change in enthalpy
**the amount of heat energy absorbed by a process that occurs at a constant pressure (-ΔH is the heat given off) - ENdothermic
-
heat ENters system
heat leaves surroundings (cool down)
**ABSORBES heat energy
(break bond) - EXothermic
-
heat EXits system
heat enters surroundings (heat up)
**gives off heat energy
(make bond) - ΔH =
-
H(final) - H(initial)
+ = endothermic
- = exothermic - entropy
-
*number of ways a system can be arranged
"S"
S(gas) >> S(liquid) > S(solid) - ΔS =
-
S(final) - S(initial)
look for:
**change of state
**few big molec. <--> many small molec.
**change in temp. - free energy change
-
ΔG
ΔG = ΔH - TΔS
if: then:
ΔG - spontaneous
ΔG + nonspontaneous
definition: energy available for a spont. process to do work; for a nonspont. process, it is the amount of energy that must be supplied to cause the process to occur. -
spontaniety of:
- endothermic reactions
- exothermic reactions -
Endothermic: (+)+(+)
- spont at high T
-nonspont at low T
Exothermic:(-)+(-)
-spont. at low T
-nonspont. at high T