01:160:162 Lecture Notes - Lecture 28: Covalent Bond

• School: Rutgers University
• Department: Chemistry
• Course: 01:160:162
• Professor: B.Langowski

Document Summary

Allotropes different structures of a given element in the same state of matter. Diamond has less s than graphite: c atoms more ordered and constrained by network covalent bonds. In graphite sheets of c atoms not as tightly bound. In thermodynamics, universe divided into a system and its surroundings. Suniv (cid:878) (cid:900)sys (cid:860) (cid:900)surr (**note: j(cid:934)(cid:932)(cid:933) (cid:900) (cid:922)(cid:926)(cid:929)(cid:925)(cid:922)(cid:918)(cid:932) (cid:900)sys) Entropy changes of a system (i. e. chemical reactions) can be calculated from standard molar entropies (s ) of reactants and products. Not (cid:929)(cid:928)(cid:932)(cid:932)(cid:922)(cid:915)(cid:925)(cid:918) (cid:933)(cid:928) (cid:917)(cid:918)(cid:933)(cid:918)(cid:931)(cid:926)(cid:922)(cid:927)(cid:918) (cid:900)surr using s . Can be determined using enthalpy changes of system (cid:857) (cid:889)sys) Let system = reaction and surroundings (air, container, table, etc) When reaction is exothermic (- (cid:889)sys) system releases its e into surroundings. Results in entropy change in surroundings entropy of surroundings increases (+) W(cid:921)(cid:918)(cid:927) (cid:931)(cid:918)(cid:914)(cid:916)(cid:933)(cid:922)(cid:928)(cid:927) (cid:922)(cid:932) (cid:918)(cid:927)(cid:917)(cid:928)(cid:933)(cid:921)(cid:918)(cid:931)(cid:926)(cid:922)(cid:916) (cid:857)(cid:860) (cid:889)sys) system absorbs e from surroundings. Results in entropy change in surroundings entropy of surroundings decreases (-)