Le Chatelier's Principle allows us to make predictions about what will happen to an equilibrium reaction when a change in concentration, pressure (volume), or temperature is applied to the system. The principle tells us that the equilibrium will shift in a way the lessens the effect of that change on the system.
Self check questions
1. Consider the reaction system, CoO(s) + H2(g) Co(s) + H2O(g) The equilibrium constant expression is:
a.
b.
c.
c.
2. Using Le Chatelier’s principle, what would be the effect of adding more nitrogen to the system?
a. the reaction would continue to go towards completion with really no change
b. the reaction would reverse it self because of the increase in nitrogen
c. the reaction would continue in the forward direction with a new equilibrium being established
d. more heat would be needed to change the “extra” amount of nitrogen into the corresponding product
c. the reaction would continue in the forward direction with a new equilibrium being established
3. Consider the same reaction and what would the effect be of increasing the temperature?
a. the reverse reaction will occur to consume some of the added energy
b. the forward reaction occurs, but at a faster rate
c. the reaction continues to go forward towards completion with really no changes
d. the extra energy will result in a different volume of gas
a. the reverse reaction will occur to consume some of the added energy
4. Given this reaction at equilibrium: 2SO2(g) + O2(g) 2SO3(g), if this equilibrium is established by beginning with equal number of moles of SO2 and O2 in a 1.0 Liter bulb, then the following must be true at equilibrium:
a. [SO2] = [SO3]
b. [SO2] < [O2]
c. 2[SO2] = 2[SO3]
d. [SO2] = [O2]
b. [SO2] < [O2]
5. Solid HgO, liquid Hg, and gaseous O2 are placed in a glass bulb and are allowed to reach equilibrium at a given temperature. 2HgO(s) 2Hg(l) + O2(g) H = +43.4 kcal The mass of HgO in the bulb could be increased by:
a. adding more Hg
b. reducing the volume of the bulb.
c. removing some Hg.
d. removing some O2.
b. reducing the volume of the bulb.
After reading both the text book and the web site, take the unit quiz20 points
Chapter 17 problem set (pages 759-765): Do the following question set for practice. Check the answers in the back of the book to make sure you are doing them correctly. Be sure to contact your teacher with questions of you are having trouble.
Free Response Question: Sulfur trioxide gas, one of the causes of acid rain, is produced in the upper atmosphere when oxygen reacts with sulfur dioxide gas in the reaction shown below:
2SO2(g) + O2(g) <--> 2SO3(g) H0 = -197kJ
The gases are placed in a reaction vessel and allowed to come to equilibrium at temperature T, pressure P, and volume V. Predict and explain the effects that each of the following will have on the equilibrium composition of the reaction:
The partial pressure of SO3(g) is increased by the addition of SO3(g).
The pressure in the vessel is increased by the addition of He.
The total pressure in the vessel is increased by decreasing the volume of the vessel.
Lab
Self check questions
Co(s) + H2O(g) The equilibrium constant expression is:
H = +43.4 kcal The mass of HgO in the bulb could be increased by:
After reading both the text book and the web site, take the unit quiz 
Chapter 17 problem set (pages 759-765): 
Lab: Equilibrium Constant 
Free Response Question: