CHEM 202
HOMEWORK 2
Chapter Two
1. Arrange the following substances in order of increasing entropy at 25
°C : (a) N2(g), (b) K(s), (c) Ar(g), (d) CO2(g), (e) CaCl2(s). Given the
reasons for your arrangement?
2. Using the data in the provided appendix, Calculate the standard
entropy changes for the following reactions at 25 °C:
(a) S(s)  O 2 ( g )  SO2 ( g )
(b) MgCO3 ( s)  MgO( s)  CO2 ( g )
3. Without consulting the provided appendix, predict whether the
entropy change is positive or negative for each of the following
reactions. Given reasons for your predictions.
(a) 2KClO 4 ( s)  2 KClO 3 ( s )  O2 ( g )
(b) H 2 O( g )  H 2 O(l )
(c) 2Na(s)  2H 2 O(l )  2 NaOH (aq)  H 2 ( g )
(d ) N 2 ( g )  2 N ( g )
4. Calculate ΔG° for the following reactions at 25 °C using the provided
appendix:
(a) N 2 ( g )  O2 ( g )  2 NO( g )
(b) H 2 O(l )  H 2 O( g )
(c) 2C 2 H 2 ( g )  5O2 ( g )  4CO2 ( g )  2 H 2 O(l )
5. From the values of ΔH and ΔS, predict which of the following
reactions would be spontaneous at 25°C : reaction A: ΔH=
10.5kJ/mol, ΔS=30J/K. mol, reaction B ΔH= 1.8kJ/mol, ΔS= -113J/K.
mol. If either of the reaction is nonspontaneous at 25 °C, at what
temperature might it become spontaneous?
6. Calculate KP for the following reaction at 25 °C:
H 2 ( g )  I 2 ( g )  2HI ( g )
G  2.60kJ/mol
CHEM 202
HOMEWORK 2
7. The molar heat of vaporization of ethanol is 39.3 kJ/mol and the
boiling point of ethanol is 78.3 °C. Calculate ΔS for the vaporization
of 0.8 mol ethanol?
8. Large quantities of hydrogen are needed for the synthesis of ammonia.
One preparation of hydrogen involves the reaction between carbon
monoxide and steam at 350 °C in the presence of a copper-zinc
catalyst:
CO( g )  H 2 O( g )  CO2 ( g )  H 2 ( g )
Using the data in the provided appendix calculate the equilibrium
constant (KP) for the reaction and the temperature at which the
reaction favors the formation of CO and H2O?
9. For the reaction
I2 (g) + H2(g)  2HI (g), G= +2.6 kJ/mol at 25C.
If P(H2) = 4.26. atm, P(I2) = 0.024atm, and P(HI) = 0.23 atm
Calculate G for this reaction.