Transcript 17

THURSDAY, DECEMBER 17TH
• Grab a green homework sheet and set of practice problems
off the projector
• Any questions about last night’s homework?
WINTER BREAK
• Mandatory
• Read and take notes on sections 19.5-19.7
• Problem set 2 (similar to problem set 1 – use it to refresh yourself
before you get back!)
• Extra Credit
• Summative section of the gradebook – up to 20 total points (10 per
chapter, ~2% overall grade increase)
• Chapters 18 and 21
• You can get partial credit
• See my website for details
Which of the following statements is true?
a)
b)
c)
d)
e)
Spontaneous reactions proceed at a fast rate.
Spontaneous reactions proceed at a slow rate.
Non-spontaneous reactions proceed at a fast rate.
Non-spontaneous reactions proceed at a slow rate.
There is no relationship between spontaneity of
a reaction and the rate of a reaction.
Which of the following statements is true?
a)
b)
c)
d)
e)
Spontaneous reactions proceed at a fast rate.
Spontaneous reactions proceed at a slow rate.
Non-spontaneous reactions proceed at a fast rate.
Non-spontaneous reactions proceed at a slow rate.
There is no relationship between spontaneity of
a reaction and the rate of a reaction.
OF THE FOLLOWING, WHICH SYSTEM SHOWS A
DECREASE IN ENTROPY?
a)
b)
c)
d)
CH3OH (l) → CH3OH (g)
NaCl (s) → Na+ (aq) + Cl– (aq)
N2 (g) + O2 (g) → 2 NO (g)
2 NO2 (g) → N2O4 (g)
OF THE FOLLOWING, WHICH SYSTEM SHOWS A
DECREASE IN ENTROPY?
a)
b)
c)
d)
CH3OH (l) → CH3OH (g)
NaCl (s) → Na+ (aq) + Cl– (aq)
N2 (g) + O2 (g) → 2 NO (g)
2 NO2 (g) → N2O4 (g)
Which of the following is ALWAYS spontaneous?
a)
b)
c)
d)
e)
C2H6O (l) + 3 O2 (g) → 2 CO2 (g) + 3 H2O (g); ΔH < 0
The sublimation of dry ice (CO2)
The freezing of water (H2O)
The formation of water from its gaseous elements
None of the above are ALWAYS spontaneous.
Which of the following is ALWAYS spontaneous?
a)
b)
c)
d)
e)
C2H6O (l) + 3 O2 (g) → 2 CO2 (g) + 3 H2O (g); ΔH < 0
The sublimation of dry ice (CO2)
The freezing of water (H2O)
The formation of water from its gaseous elements
None of the above are ALWAYS spontaneous.
PREDICT THE CONDITIONS UNDER WHICH THE
FOLLOWING REACTION IS SPONTANEOUS:
SF6 (g) → SF6 (l)
a)
b)
c)
d)
e)
High temperature
Low temperature
This reaction is always spontaneous.
This reaction is always non-spontaneous.
Not enough information to predict
PREDICT THE CONDITIONS UNDER WHICH THE
FOLLOWING REACTION IS SPONTANEOUS:
SF6 (g) → SF6 (l)
a)
b)
c)
d)
e)
High temperature
Low temperature
This reaction is always spontaneous.
This reaction is always non-spontaneous.
Not enough information to predict
When one mole of liquid water is frozen in a freezer at
–10°
C, what are the relative values of ΔSsys and ΔSsurr?
Is the reaction spontaneous?
a)
b)
c)
d)
e)
ΔSsys > 0, ΔSsurr < 0, spontaneous
ΔSsys > 0, ΔSsurr < 0, non-spontaneous
ΔSsys > 0, ΔSsurr < 0, equilibrium
ΔSsys < 0, ΔSsurr > 0, spontaneous
ΔSsys < 0, ΔSsurr > 0, non-spontaneous
When one mole of liquid water is frozen in a freezer at
–10°
C, what are the relative values of ΔSsys and ΔSsurr?
Is the reaction spontaneous?
a)
b)
c)
d)
e)
ΔSsys > 0, ΔSsurr < 0, spontaneous
ΔSsys > 0, ΔSsurr < 0, non-spontaneous
ΔSsys > 0, ΔSsurr < 0, equilibrium
ΔSsys < 0, ΔSsurr > 0, spontaneous
ΔSsys < 0, ΔSsurr > 0, non-spontaneous
PROBLEM SET 1
• Key equations:
• On formula sheet
°
°
• Σ𝑆𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠
− Σ𝑆𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠
• Not on formula sheet
• Δ𝑆𝑠𝑢𝑟𝑟 =
• Δ𝑆𝑠𝑢𝑟𝑟 =
−𝑞𝑠𝑦𝑠
𝑇
−Δ𝐻𝑠𝑦𝑠
𝑇
(only at constant P!)