a.) Consider the reaction:
4HCl (aq) + MnO2 (s) <--> Cl2 (g) + 2 H2O (l) + MnCl2 (aq) Delta (H)degree
The equilibrium is dsplaced to the left if:
a. Catalyst is added
b. pressure is lowered
c. temp is lowered
d. H2O is added
e. none of these
* I know it is not a, b, or c, but i don't know about d.
b.) Consider the following gas phase reaction at 25 oC. N2 (g) + C2H2 (g) <---->
2HCN(g) 1.600 mol N2 (g) and 1.750 mol C2H2 (g) are placed in a 1.000 L
vessel and the mixture is allowed to react. At equilibrium, there are 1.587 mol N2
(g) in the mixture. What is Kc for this reaction at 25 oC?
a) d is the correct answer. Because water is produced as the result of reaction, if water is
added from outside, the reaction will be shifted towards the left.
b) Kc =
HCN 2
N 2 C 2 H 2 
Since 1.587 moles of N2 are present at equilibrium, moles of N2 reacted = 1.6 -1.587 =
0.013 moles. 0.013 moles of N2 would react with 0.013 moles of C2H2 to produce 0.026
moles of HCN
Initial Concentration
Reacted Concentration
Equilibrium Concentration
Now Kc =
HCN 2
N 2 C 2 H 2 
=
N2
1.6
0.013
1.587
C2H2
1.75
0.013
1.737
HCN
------------0.026
(0.026) 2
 0.000245
(1.587)(1.737)