GENERAL CHEMISTRY 2 -FOURTH
QUARTER-Spontaneous Change & GIBBS
FREE ENERGY
theajeanise.pido@iloilonhs.edu.ph Switch account
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theajeanise.pido@iloilonhs.edu.ph
FAMILY NAME, FIRST NAME MI *
PIDO, THEA JEANISE S.
STRAND, GRADE LEVEL, SECTION *
STEM 12-C
READ EACH ITEM CAREFULLY AND CLICK THE CORRECT ANSWER
Activity 1. Spontaneous Process
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Dissolving salt table salt (NaCl) in hot soup
1 point
Spontaneous
Nonspontaneous
Clear selection
Compare each pair and tell which one is more spontaneous than the other. *
1 point
Rock rolled downhill
Rock rolled uphill
Climbing Mt. Everest *
1 point
Spontaneous
Nonspontaneous
Iron exposed to water and oxygen forms rust *
1 point
Spontaneous
Nonspontaneous
Heat flows from a hotter object to a colder one *
1 point
Spontaneous
Nonspontaneous
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Compare each pair and tell which one is more spontaneous than the other. *
1 point
Dowhhill skiing
Uphill Skiing
Spreading fragrance in a room by removing the cap from a perfume bottle *
1 point
Spontaneous
Nonspontaneous
Activity 2. Entropy: An Introduction to Chaos
Choose the one having the larger standard entropy at 25ºC. *
1 point
2Cl(g)
Cl2(g)
How does the entropy of the system changes when liquid water forms from *
1 point
gaseous hydrogen and oxygen?
increasing entropy
decreasing entropy
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Predict the sign of ΔSsys for each of the following reactions using the
qualitative ideas discussed
*
1 point
+ΔSsys
-ΔSsys
How does the entropy of the system changes when liquid wax solidifies? *
1 point
increasing entropy
decreasing entropy
How does the entropy of the system changes when dry ice sublimes? *
1 point
increasing entropy
decreasing entropy
Predict the sign of ΔSsys for each of the following reactions using the
qualitative ideas discussed
*
1 point
+ΔSsys
-ΔSsys
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Predict the sign of ΔSsys for each of the following reactions using the
qualitative ideas discussed
*
1 point
*
1 point
How does the entropy of the system changes when dissolving table salt in *
1 point
+ΔSsys
-ΔSsys
How does the entropy of the system changes when dew forms from water
vapor?
increasing entropy
decreasing entropy
water?
increasing entropy
decreasing entropy
Predict the sign of ΔSsys for each of the following reactions using the
*
1 point
qualitative ideas discussed
+ΔSsys
-ΔSsys
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Choose the one having the larger standard entropy at 25ºC. *
1 point
SiO2(s)
CO2(g)
Choose the one having the larger standard entropy at 25ºC. *
1 point
Ag+(g)
Ag+ (aq)
Predict the sign of ΔSsys for each of the following reactions using the
*
1 point
*
1 point
qualitative ideas discussed
+ΔSsys
-ΔSsys
Predict the sign of ΔSsys for each of the following reactions using the
qualitative ideas discussed
+ΔSsys
-ΔSsys
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Predict the sign of ΔSsys for each of the following reactions using the
qualitative ideas discussed
*
1 point
+ΔSsys
-ΔSsys
Choose the one having the larger standard entropy at 25ºC. *
1 point
BaSO4(s)
BaSO4(aq)
Predict the sign of ΔSsys for each of the following reactions using the
qualitative ideas discussed
*
1 point
+ΔSsys
-ΔSsys
Choose the one having the larger standard entropy at 25ºC. *
1 point
CS2(s)
CS2(l)
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Predict the sign of ΔSsys for each of the following reactions using the
*
1 point
*
1 point
qualitative ideas discussed
+ΔSsys
-ΔSsys
Predict the sign of ΔSsys for each of the following reactions using the
qualitative ideas discussed
+ΔSsys
-ΔSsys
Activity 3. The Second Law
The solubility of silver chloride is so low that it precipitates spontaneously *
2 points
from many solutions. The entropy change of the system is negative for this
process. Ag+ (aq) + Cl-(aq) —> AgCl(s) ΔH°rxn = -65 kJ . Since ΔS
decreases in this spontaneous reaction, shouldn’t the reaction be
nonspontaneous?
YES
N0
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Liquid water vaporizes spontaneously at 25ºC. What is the sign of ΔSuniv? *
2 points
Decide on the relative sizes of ΔSsys and ΔSsurr and give their signs.
ΔSuniv *(+) / ΔSsys (+) and ΔSsurr (+)
ΔSuniv *(-) / ΔSsys (+) and ΔSsurr (-)
ΔSuniv *(-) / ΔSsys (-) and ΔSsurr (-)
ΔSuniv *(+) / ΔSsys (-) and ΔSsurr (-)
Activity 4. Calculation of the Entropy Change for a Reaction
Determine ΔSºrxn for the reaction:
Given:
H2SO4(l) —> SO3(g) + H2O(l) *
S°: H2SO4(l) = 156.9 J/K•mol
3 points
S°: SO3(g) = 256.2 J/K•mol S°: H2O(l) = 69.9 J/K•mol
ΔSºrxn = -169.2 J/K•mol
ΔSºrxn = +169.2 J/K•mol
ΔSºrxn = +343.2 J/K•mol
ΔSºrxn = -343.2 J/K•mol
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The standard entropies for some substances at 25ºC are KBrO3(s)
J/K.mol O2(g)
*
3 points
*
2 points
S°= 149.2 J/K.mol KBr(s) S°= 96.4
S°= 205.0 J/K.mol 2pts
Calculate ΔSºrxn for the reaction: 2KBrO3(s) —> 2KBr(s) + 3O2(g)
ΔSºrxn = +254.7 J/K•mol
ΔSºrxn = +509.4 J/K•mol
ΔSºrxn = +152.2 J/K•mol
ΔSºrxn = -152.2 J/K•mol
READ EACH ITEM CAREFULLY. CLICK THE CIRCLE OF YOUR ANSWER.
When the situation is indeterminate, a low temperature favors the
(____________) factor, and a high temperature favors the (____________)
factor.
enthalpy, entropy
entropy, enthalpy
enthalpy, enthalpy
entropy, entropy
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What is the standard free energy change, ∆G˚, in kJ, for the following
*
3 points
2 pts What would be the sign of ∆G (Gibbs free energy), if ∆H is + and ∆S *
2 points
reaction at 298K? Is the reaction spontaneous?
C2H5OH(l) +
∆Gf˚
kJ/mol
175
3O2(g) —> 2CO2(g)
0
-394
+
3H2O(g)
-229
+1300kJ/mol, NONSPONTANEOUS
-1300kJ/mol, SPONTANEOUS
+448kJ/mol, NONSPONTANEOUS
-448kJ/mol, SPONTANEOUS
is +
∆G + ; reaction is spontaneous at high temperature
∆G + ; reaction is nonspontaneous at high temperature
∆G – ; reaction is spontaneous (at high temperature)
∆G – ; reaction is nonspontaneous at high temperature
Under what conditions will a reaction with a decreasing entropy be
*
2 points
spontaneous or thermodynamically favorable?
If the reaction releases heat, exothermic, ∆H is negative
If the reaction releases heat, endothermic, ∆H is negative
If the reaction releases heat, exothermic, ∆H is positive
If the reaction releases heat, endothermic, ∆H is positive
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Copper(I) sulfide reacts with sulfur to produce copper(II) sulfide at 25°C.
The process is exothermic (ΔH˚ = -26.7 kJ/mol) with a decrease in
*
3 points
Is the reaction spontaneous at 298K and 1atm? CO(NH2)2 aq + H2O(l) —> *
3 points
disorder (ΔS˚ = -19.7 J/(mol•K)). Determine the thermodynamic favorablity
of the reaction by calculating ΔG˚.
Cu2S(s) + S(s) → 2CuS(s)
+20.83kJ/mol, spontaneous reaction
-20.83kJ/mol, spontaneous reaction
+20.83kJ/mol, nonspontaneous reaction
-20.83kJ/mol, nonspontaneous reaction
CO2 (g) + 2NH3 (g)
∆Hº = 119kJ
∆Sº = 354.8 J/K
T = 25ºC
+13.27kJ/mol , spontaneous reaction
-13.27kJ/mol , spontaneous reaction
+13.27kJ/mol , nonspontaneous reaction
-13.27kJ/mol , nonspontaneous reaction
2 pts What would be the sign of ∆G (Gibbs free energy), if ∆H is – and ∆S *
2 points
is –
∆G + ; reaction is spontaneous at low temperature
∆G + ; reaction is nonspontaneous at low temperature
∆G – ; reaction is spontaneous at low temperature
∆G ¬– ; reaction is nonspontaneous at low temperature
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Calculate the ∆Gº for the reaction of graphite and predict whether the
reaction is spontaneous or not:
2C(graphite) +
H2(g)
—>
C2H2(g)
*
3 points
Use Table 2.1 of
SLM for Gf
+209.2kJ/mol , nonspontaneous reaction
-209.2kJ/mol , nonspontaneous reaction
+209.2kJ/mol , spontaneous reaction
-209.2kJ/mol , spontaneous reaction
What would be the sign of ∆G (Gibbs free energy), if ∆H is + and ∆S is – *
2 points
∆G + ; reaction is spontaneous
∆G + ; reaction is nonspontaneous
∆G ¬– ; reaction is spontaneous
∆G – ; reaction is nonspontaneous
Under what conditions will an endothermic reaction be spontaneous or
*
2 points
thermodynamically favorable?
If the reaction increases entropy, ∆S is negative
If the reaction increases entropy, ∆S is positive
If the reaction decreases entropy, ∆S is positive
If the reaction decreases entropy, ∆S is negative
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2 pts What would be the sign of ∆G (Gibbs free energy), if ∆H is – and ∆S *
2 points
is +
∆G + ; reaction is spontaneous
∆G + ; reaction is nonspontaneous
∆G – ; reaction is spontaneous
∆G – ; reaction is nonspontaneous
An exothermic reaction is nonspontaneous or thermodynamically
*
2 points
unfavorable under what conditions of temperature and entropy change?
If entropy is increasing and the temperature is low
If entropy is increasing and the temperature is high
If entropy is decreasing and the temperature is low
If entropy is decreasing and the temperature is high
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