Download P2-Equilibrium Activity

MM Poster Lab1
C.1.4,C.7.6;NOS6,9,10,11;RS7;WS4-10
Chemical Equilibrium
Poster Project Topic 2
Chemistry 1
Name: ___________________________
Class Period:_________________
Introduction:
Not all chemical reactions reach completion where the limiting reactant is consumed completely.
In fact, most chemical reactions that occur in living systems never reach completion. Rather, they produce
some amount of product then appear to stop reacting in the forward direction, never fully consuming the
limiting or excess reactants. Chemical equilibrium occurs when a reaction and its reverse reaction
proceed at the same rate in a closed system. Reactions that attain the condition of chemical equilibrium
are said to be reversible reactions; meaning, the products can react to re-form the reactants under the
conditions of the reaction. The Law of Mass Action (Guldberg-Waage, 1864) postulates that the
coefficients of a balanced chemical equation can be used to describe the ratio of reactants to products for a
system at equilibrium. From the “Law of Mass Action,” the equilibrium constant can be expressed for the
c
d
general reaction:
C D
aA + bB ⇄ cC + dD
as: K
a
b
A
B
The equilibrium constant, K, is then defined as the ratio of unchanging product and reactant
concentrations for a system at equilibrium according to the ratio of reactants to products described by their
reaction ratios.
Activities:
1. Investigating chemical equilibrium:
1.1. Apply the Law of Mass Action to write the equilibrium expression for the following reactions.
1.1.1. N2O4 (g) ⇄ 2NO2 (g)
1.1.2. HSO4-(aq) + H2O ⇄ SO4 2- (aq)+ H3O+(aq)
1.1.3. H2(g) + I2(g) ⇄ 2HI(g)
1.2. Calculate the equilibrium constant for the production of hydrogen moniodide at 25oC, if the
following concentrations were determined at equilibrium.
[HI] = 3.1 x 10-2 mol/L
[I2] = 8.5 x 10-1 M
[H2] = 3.1 x 10-3 M
1.3. Using the equilibrium constant from the previous problem, calculate the concentration of
hydrogen moniodide if the concentrations of hydrogen and iodine reactants were both changed to
5.0 x 10-3 M under the same conditions. (Hint: use the same K)
Going Further:
2. Complete the following.
2.1. Fritz Haber developed an advanced method for the reaction of elemental nitrogen with elemental
hydrogen to produce ammonia at a time when the German army needed ammonia for the
production of munitions. Later the process developed by Haber was used by the U.S. to produce
agricultural fertilizer, helping to make the U.S. an agricultural leader in the world economy.
2.1.1. Write the balanced chemical equation for the production of ammonia gas from its elemental
gases.
2.1.2. Write the equilibrium expression for the Haber process of ammonia production.
2.1.3. At 500oC, the equilibrium concentrations are found to be 0.602 M nitrogen, 0.402 M
hydrogen and 0.133 M ammonia. What is the equilibrium constant value at this temperature?
Show your work.
2.2. Henri Louis Le Châtelier was an important scientist in the development of our modern
understanding of chemical equilibrium. Use the internet to research and write an informative
paragraph on Le Châtelier’s principle; stating that if a system is at equilibrium is subjected to a
stress, the equilibrium is shifted in the direction that tends to relieve the stress. Be sure to give
examples of stresses and how equilibrium is affected. Collect information from a minimum of
two sources and list your sources below your paragraph. Your paragraph should be written on a
separate piece of paper and attached.