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CHMY 361: How to Estimate Your Final Grade and Review of Thermodynamics Concepts, Slides of Physical Chemistry

ACS Standard Physical Chemistry Exam with solved Questions.

Typology: Slides

2018/2019

Uploaded on 02/11/2022

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butterflymadam ๐Ÿ‡บ๐Ÿ‡ธ

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ACS Standard
Physical Chem
Exam Taken
Tuesday by
21 students
Score %
33 55.0
32 53.3
32 53.3
32 53.3
31 51.7
29 48.3
28 46.7
28 46.7
27 45.0
27 45.0
26 43.3
25 41.7
24 40.0
23 38.3
22 36.7
21 35.0
19 31.7
19 31.7
18 30.0
16 26.7
16 26.7
Average
25.1 41.9 %
Last Year
38.6%
Nat. Avg.
52 %
pf3
pf4
pf5
pf8
pf9
pfa
pfd
pfe
pff
pf12
pf13

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Download CHMY 361: How to Estimate Your Final Grade and Review of Thermodynamics Concepts and more Slides Physical Chemistry in PDF only on Docsity!

ACS Standard Physical Chem Exam Taken Tuesday by 21 students

Score % 33 55. 32 53. 32 53. 32 53. 31 51. 29 48. 28 46. 28 46. 27 45. 27 45. 26 43. 25 41. 24 40. 23 38. 22 36. 21 35. 19 31. 19 31. 18 30. 16 26. 16 26. Average 25.1 41.9 % Last Year 38.6% Nat. Avg. 52 %

CHMY 361 How to estimate your final grade Handout

December 7, 2017 Total points = 700; Homework is worth 100; midterms = 100 each, and final = The total possible homework points =150 , so: Total % = (total HW/150 * 100 + total exam points )/700 (after including your Final)

Last yearโ€™s letter grades were typical, but could be slightly different this year. T Total % Grade (Estimate) 90-100 A 86-89 A- 80-85 B+ 75-80 B 70-74 B- 68-70 C+ 63-67 C 60-62 C- 50-59 D

A little quiz

System = insulated room with weight lifter

Weight lifter works out and the room heats up

from 20o^ C to 25 o^ C

Are โˆ† U, q, w positive, zero, or negative?

Always True Conditional

โˆ†U = q + w

Adiabatic: q = 0 ; โˆ†U = w ; Constant V:

โˆ†U = C (^) v (T 2 -T 1 ) if Cv constant For ideal gas the above is always true (even if volume changes)

H = U + PV

โˆ†H = โˆ†U + P 2 V 2 - P 1 V 1

For P=Pext = constant and PV work only:

โˆ†H = q =

โˆ†H = C (^) P (T 2 -T 1 ) if C (^) P constant For ideal gas the above is always true (even if pressure changes)

for Pext constant: wpv = -Pext (V 2 โ€“ V 1 ) ;

if isothermal reversible and ideal gas:

Solids and Liquids (volume changes are very small) Cp โ‰… Cv and โˆ†H โ‰… โˆ†U

โˆ† H T C dTp

T = (^) โˆซ (^1)

2

dw

w

pv

pv

= โˆ’

= โˆ’ (^) โˆซ

P dV

P dV

ext

V ext

V

1

2

w (^) pv = โˆ’ (^) โˆซ PdV = โˆ’ nRT V V V

V (^) ln 2 (^11)

2

U C dT

T โˆ† =โˆซ T 2

1 v

Reversible Isothermal PV work (ideal gas)

p ext = p = nRT/V (balanced forces)

ONLY if p = pext = and ideal gas (but is common case)

2

1

2

1

2

1

V

V

V

V

V

V

dV

V

nRT

w pextdV pdV

Sum of fractional changes = natural logarithm

ln

V

V

nRT

V

dV

w = โˆ’ nRT = โˆ’

2

1

V

V

An integral is just a

Sum

What are โˆ† U and q?

โˆ† U =0 (isothermal, ideal gas), therefore q = -w

  • 361 Lec
  • Tue 14sep
NOOOO

At constant T and P, the Gibbs Free Energy is king.

Definition: G = H-TS

โˆ† G = โˆ† H- โˆ† (TS) always true

But, most useful for constant T and P=Pext = constant

so that: โˆ† (PV) =P โˆ† V and โˆ† (TS) = T โˆ† S; then

โˆ† G = โˆ† U + p โˆ† V - T โˆ† S = q - Pext โˆ† V + w (^) useful + p โˆ† V - T โˆ† S

but, โˆ† S surr = -q/T so q = -T โˆ† S surr

โˆ† G = -T( โˆ† S + โˆ† Ssurr) + w (^) useful

โˆ† G = -T โˆ† S (^) univ + w (^) useful if T and p constant

361 Lec 12 Mon 20sep

non-PV

(โ€œotherโ€) work

(w = - p (^) ext โˆ† V + w (^) useful )