CHM 2046 Quiz 3A March 31, 2006
Answer all questions. Look at the end for useful information.
1. Consider the two reactions below.
2 Mg (s) + O (2) → 2 MgO (s) ΔG° = 1138 kJ
CO 2g) → CO (g) + ½O (g) 2 ΔG° = + 257 kJ
a) (4 points) What is the resulting reaction obtained from coupling the above reactions together (no
O 2(g) should appear)?
b) (4 points) What is ΔG° for the reaction in part a)?
2. The reaction below at 298 K has an equilibrium constant of 3.89 x 10 . 34
2 HCl (g) ⇌ H (g2 + Cl (g2
a) (2 points) Does the equilibrium lie far to the left, far to the right, or somewhere near the middle?
The equilibrium lies ( ).
b) (7 points) Calculate ΔG° for this reaction.
c) (7 points) What is ΔG for this reaction at 300 K when the partial pressures (p) of each species are
as follows: p(HCl) = 0.2 atmospheres, p(H ) = 3 a2mospheres, p(Cl ) = 0.4 at2ospheres?
d) (4 points) Calculate ΔG° for the reaction below at 298 K:
2 NOCl (g) → 2 NO (g) + Cl (g) 2
ΔH° vafues (kJ/mol): NO(g) = 90.29 Cl (g) = 0200 NOCl (g) = 51.71
S° values (J/mol.K): NO(g) = 210.7 Cl (g) 2 223.1 NOCl(g) = 261.1
ΔG° falues (kJ/mol): NO(g) = 86.5 Cl (g) =20.0 NOCl (g) = 66