WorksheetsAP Chemistry Spontaneity, Entropy, and Free Energy
Total questions: 10
Worksheet time: 5mins
The thermodynamic quantity that expresses the degree of disorder in a system is _
entropy
internal energy
heat flow
enthalpy
bond energy
Which one of the following is always positive when a spontaneous process occurs?
ΔH univ
ΔH surr
ΔS surr
ΔS univ
ΔS sys
ΔS will be positive for the reaction
2H2 (g) + O2 (g) -> 2H2O (g)
2NO2 (g) -> N2O4 (g)
BaF2 (s) ->Ba2+ (aq) + 2F- (aq)
2Hg (l) + O2 (g) ->2HgO (s)
Which one of the following processes produces a decrease in the entropy of the system?
dissolution of solid KCl in water
mixing of two gases into one container
freezing water to form ice
melting ice to form water
Of the following, the entropy of gaseous __________ is the largest at 25eC and 1 atm.
C2H2
H2
C2H6
CH4
C2H
What can be said about a chemical system that has reached a minimum in free energy?
The system has achieved equilibrium.
The reaction is complete.
The system entropy is zero.
The reaction is very fast.
For the reaction C2H6 (g) ->C2H4 (g) + H2 (g) ΔHο is +137 kJ/mol and ΔDSοis +120 J/K œ mol. This reaction is
nonspontaneous at all temperatures
unreliable
spontaneous only at high temperature
spontaneous at all temperatures
spontaneous only at low temperature
A reaction that is not spontaneous at low temperature can become spontaneous at high temperature if ΔH is __________ and ΔS is __________.
+, +
-, -
+, -
-, +
+, 0
For a reaction to be spontaneous under standard conditions at all temperatures, the signs of ΔHΟ and ΔSΟ must be __________ and __________, respectively.
+, +
+, -
-, +
-, -
+, 0
In the Haber process, ammonia is synthesized from nitrogen and hydrogen: N2 (g) + 3H2 (g) ->2NH3 (g)
∆G at 298 K for this reaction is -33.3 kJ/mol.
The value of ∆G at 298 K for a reaction mixture that consists of 1.9 atm N2, 1.6 atm H2, and 0.65 atm NH3 is
3.86 x103
-1.8
-40.5
-7.25 x103
-104.5
