Chapter+6 - Click to edit Master subtitle style 6/6/11...

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Unformatted text preview: Click to edit Master subtitle style 6/6/11 Chapter 6 Thermochemistry Chemistry The Molecular Nature of Matter and Change Dr. Shamindri M. Arachchige [email protected] Davidson 11 1 Office Hours: Location: Davidson 11 Monday 1:45-4:45 PM Wednesday 1:45-4:15 PM Other hours by appointment 11 6/6/11 Chapter 6 Thermochemistry Thermodynamics: Thermochemistry: System Surroundings 22 6/6/11 Chapter 6 Thermochemistry First Law of Thermodynamics First Law: Potential Energy ⇔ Kinetic Energy Potential Energy: Kinetic Energy: Internal Energy: Units of Energy 33 6/6/11 Chapter 6 Thermochemistry ∆ E = E final- E initial = E products- E reactants 44 Units of energy: 6/6/11 55 Chapter 6 Thermochemistry q = w = E = q + w Δ 6/6/11 66 Chapter 6 Thermochemistry Chem 1036 Chapter 6 1 of 1 Work (w) Pressure-volume work: Work of expansion: Δ V = V final – V initial = Net increase in moles of gas: Work of contraction: Δ V = V final – V initial = Net decrease in moles of gas: 6/6/11 77 Chapter 6 Thermochemistry work = ( ─ ) work = (+) Δ V = Δ V = Units of work: w = P V ─ ∆ 6/6/11 88 Chapter 6 Thermochemistry 6/6/11 99 E x a m p l e P r o b l e m : C o n s i d e r t h e f o l l o w i n g r e a c t i o n s . D o e s t h e s y s t e m d o w o r k o n t h e s u r r o u n d i n g s o r d o e s t h e s u r r o u n d i n g s d o w o r k o n t h e s y s t e m ? a . C 2 H 2 ( g ) + 2 H 2 ( g ) → C 2 H 6 ( g ) b . 2 N 2 O 5 ( g ) → 4 N O 2 ( g ) + O 2 ( g ) E x a m p l e P r o b l e m : A g a s i s h e a t e d , c a u s i n g i t t o e x p a n d f r o m a v o l u m e o f 2 . 0 L t o 4 . 5 L a t 1 a t m p r e s s u r e . C a l c u l a t e t h e w o r k o f t h e s y s t e m i n j o u l e s ( w a t c h t h e s i g n ) . 1 0 1 . 3 J = 1 L • a t m Chapter 6 Thermochemistry 6/6/11 1010 Chapter 6 Thermochemistry Example Problem : A gas is heated, causing it to expand from a volume of 2.0 L to 4.5 L at 1.0 atm pressure. Calculate the work of the system in joules (watch the sign). 101.3 J = 1 L • atm 6/6/11 1111 Chapter 6 Thermochemistry Heat (q) Heat: Example: 2 Al(s) + Fe 2 O 3 (s) → 2 Fe(s) + Al 2 O 3 (s) Exothermic: 6/6/11 1212 Chapter 6 Thermochemistry E x a m p l e : B a ( O H ) 2 ( s ) + 2 N H 4 S C N ( s ) → B a ( S C N ) 2 ( a q ) + 2 N H 3 ( a q ) + 2 H 2 O E n d o t h e r m i c : R e a c t a n t s R e a c t a n t s P r o d u c t s P r o d u c t s q < O E x o t h e r m i c q > O E n d o t h e r m i c Heat (q) Heat (q) E x a m p l e : B a ( O H ) 2 ( s ) + 2 N H 4 S C N ( s ) → B a ( S C N ) 2 ( a q ) + 2 N H 3 ( a q ) + 2 H 2 O E n d o t h e r m i c : R e a c t a n t s R e a c t a n t s...
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This note was uploaded on 06/06/2011 for the course CHEM 1036 taught by Professor Amateis during the Spring '08 term at Virginia Tech.

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Chapter+6 - Click to edit Master subtitle style 6/6/11...

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