Humboldt State University ® Department of Chemistry

Richard A. Paselk

 

General Chemistry

Spring 2009

Exercise: Reaction Diagrams & Chemical Equilibrium

© R. Paselk 2009
 
 

Discussion Modules

 

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Reaction Progress Diagrams


1. Consider the reaction

Reactants equilibrium arrow Products + Energy

Draw a reaction coordinate diagram for this reaction and label it completely.

2. Consider the reaction

Reactants + Energy equilibrium arrow Products

Draw a reaction coordinate diagram for this reaction and label it completely.

3 a. Consider the catalyzed reaction

Reactants equilibrium arrow Products + Energy

Draw a reaction coordinate diagram for this reaction showing the uncatalyzed and catalyzed reaction curves. Label the axis, and the two curves:

b. Consider the catalyzed reaction

Reactants equilibrium arrow Products + Energy

Draw a reaction coordinate diagram for this reaction as above but add the activation energy, Ea, on the appropriate curve in this diagram and label it.

c. Consider the catalyzed reaction

Reactants equilibrium arrow Products + Energy

Draw a reaction coordinate diagram for this reaction as above but add the activation energy, Ea, for the catalyzed reaction on the appropriate curve in this diagram and label it.

d. Consider the catalyzed reaction

Reactants equilibrium arrow Products + Energy

Draw a reaction coordinate diagram for this reaction as above but this time show the free energy difference. Is DeltaG positive or negative?

e. Consider the catalyzed reaction

Reactants equilibrium arrow Products + Energy

Draw a reaction coordinate diagram for this reaction as above but this time label the reactants, the products and the transition state(s). How many are there on this diagram? How many for each curve?

f. Consider the catalyzed reaction

Reactants equilibrium arrow Products + Energy

Draw a reaction coordinate diagram for this reaction as above but this time label completely.


 

Chemical Equilibrium Problems


1. Consider the reaction

N2(g) + 3H2(g) equilibrium arrow 2NH3(g) + 92.2 kJ

Note that heat appears on the product side - the system is giving up heat, therefore DeltaH is negative, DeltaH = - 92.2 kJ

Using Le Châtelier's Principle, predict what will happen to [NH3] if:

Predict how the equilibrium will shift (right, left, or neither) if:

2. Consider the gas phase reaction at equilibrium :

PCl5 equilibrium arrow PCl3 + Cl2

What will happen to this reaction if the volume is increased?

What will happen to this reaction if chlorine (Cl2) is added?

 

3. Consider the gas phase reaction:

2 HI equilibrium arrow H2 + I 2

Keq = 2.06 x 10-2 @ 458°C

If both hydrogen and iodine are measured to have concentrations of 0.0135 M each at 458°C, what is the concentration hydrogen iodide?

4. Consider the gas phase reaction:

2 HBr equilibrium arrow H2 + Br2

Keq = 1.5 x 10-5 @ 1400 K

Calculate the concentrations of all species at equilibrium if we start with 0.15 moles each of hydrogen bromide and bromine in a 0.500 L container at 1400 K.

5. Consider the gas phase dissociation of carbon dioxide to carbon monoxide and oxygen @ 1000 K.

If 0.200 moles of carbon dioxide is placed in a 1.00 L container at 1000 K calculate the concentrations of all species at equilibrium. Keq = 4.5 x 10-23 @ 1000 K.

Answers 1-3 & 1-5


In addition to these exercises you should familiarize yourself with text materials.


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© R A Paselk

Last modified 20 November 2009