Chemistry, The Central Science, 11th edition
Theodore L. Brown; H. Eugene LeMay, Jr.;
Bruce E. Bursten and Catherine J. Murphy
Chapter 19
Chemical Thermodynamics
Donna Narsavage Heald
Siena College
Loudonville, NY
 2009, Prentice Hall
Which substance will have
the highest entropy?
1.
2.
3.
4.
5.
Butane
Isobutane
Pentane
Isopentane
Neopentane
Which substance will have
the highest entropy?
1.
2.
3.
4.
5.
Butane
Isobutane
Pentane
Isopentane
Neopentane
Which process will have a negative DS?
1. Dissolving a substance
2. Melting
3. Falling leaves
4. Oxidation of a metal
5. Decomposition of water into H2 and O2
Which process will have a negative DS?
1. Dissolving a substance
2. Melting
3. Falling leaves
4. Oxidation of a metal
5. Decomposition of water into H2 and O2
A reaction will be spontaneous at lower
temperatures when the sign
of DH and DS is
A reaction will be spontaneous at lower
temperatures when the sign
of DH and DS is
If the temperature of the reaction is decreased, what is
the effect on the equilibrium constant and DG?
N2(g)
1.
2.
3.
4.
5.
+
3 H2(g)
K increases; DG increases.
K decreases; DG decreases.
K increases; DG decreases.
K decreases; DG increases.
Temperature does not affect
equilibrium or DG.
2 NH3(g)
DH° = –92.4 kJ/mol
If the temperature of the reaction is decreased, what is
the effect on the equilibrium constant and DG?
N2(g)
1.
2.
3.
4.
5.
+
3 H2(g)
K increases; DG increases.
K decreases; DG decreases.
K increases; DG decreases.
K decreases; DG increases.
Temperature does not affect
equilibrium or DG.
2 NH3(g)
DH° = –92.4 kJ/mol
Upon heating, limestone (CaCO3) decomposes to CaO
and CO2. Speculate on the sign of DH and DS for this
process.
CaCO3(s)
CaO(s)
+
CO2(g)
Upon heating, limestone (CaCO3) decomposes to CaO
and CO2. Speculate on the sign of DH and DS for this
process.
CaCO3(s)
CaO(s)
+
CO2(g)