Name: _________________________________________
Date:____________________________
Homework 9 – Optional – Do Not turn in – not for credit!
1. Given: 3NO2 (g) + H2O (l) → 2HNO3 (l) + NO (g)
Calculate the rate of formation of HNO3 and NO if NO2 is consumed at the rate 0f 0.25 mole/Lsec.
What is the rate that H2O is consumed if NO2 is consumed at 0.25 mole/Lsec
2. After 2.5 minutes, what are the concentrations of HNO3 and NO?
3. Why is there a negative sign placed in front of the reaction rates that are written for the reactants?
4. What is the difference between the average rate and the instantaneous rate?
5. For each of the following reactions, determine the reaction order with respect to each reactant and
calculate the overall reaction order:
a. NO (g) + Cl2 (g) → 2NOCl (g)
rate = k[NO]2[Cl2]
b. 5Br-1 (aq) + BrO3-1 (aq) + 6H+1 (aq) → 3Br2 (l) + 3H2O (l) rate = k[Br-1][BrO3-1][H+1]2
c. O2 (g) + 2NO (g) → 2NO2 (g) rate = k[O2][NO]2
6.) The following initial rates were obtained for the reaction:
2NO (g) + O2 (g) → 2NO2 (g)
Run
1
2
3
[NO] M
0.0240
0.0150
0.0240
[O2] M
0.0350
0.0350
0.0450
Find the reactant order
Determine the rate law
Determine the overall reaction order
Rate (mole/Lsec)
0.143
0.0559
0.184
Decomposition of Nitrogen Dioxide Gas
Concentration f Nitrogen Dioxide (mole/L)
0.02
0.018
0.016
0.014
0.012
0.01
0.008
0.006
0.004
0.002
0
0
10
20
30
40
50
60
70
Time (sec)
7.)
Using the plot given above, draw a best fit line (curve!) indicating the reaction curve as the NO2
gas decomposes as given by the equation:
2NO2 (g) → 2NO (g) + O2 (g)
Calculate the instantaneous rate at 35 sec and at 20 sec
SHOW ALL WORK!!
(your answer may differ slightly from one another’s . . . )
8.) The following rates were obtained for the reaction
2I-1 (aq) + S2O8-2 (aq) → I2 (aq) + 2SO4-2 (aq) at 25oC
I-1 (M)
0.15
0.15
0.50
Run
1
2
3
S2O8-2 (M)
0.45
0.25
0.45
Rate (mole/Lsec)
2.6 x 10-4
1.4 x 10-4
8.6 x 10-4
Find the rate law for this reaction. Determine k with the correct units!!
9. The acid catalyzed decomposition of thiosulfate in the presence of dissolved oxygen is:
2S2O3
-2
+
[H ]
(aq)
+ O2 (g) → 2SO4-2 + 2S (s)
The reaction is first order in thiosulfate ion, zero order in dissolved oxygen, and first order with respect to the
hydrogen ion. Write the rate law:
10. Using the data below and the following reaction, calculate the rate constant:
2NO (g) + 2H2 (g) → N2 (g) + 2H2O (g) at 866oC
Rate = k[H2][NO]2
Run
1
2
3
NO (M)
0.10
0.10
0.30
H2 (M)
0.010
0.040
0.010
Rate (mole/Lsec)
0.062
0.246
0.588
If your last name begins with a letter A through L calculate k based on the data given in Run1. If your last
name begins with the letter M – R calculate k based on the data based on Run 2. If your last name begins
with the letter S – Z calculate k based on the data in Run 3. Find someone with a last name other than your
letter and record their name and their k value.
11. Given the following data, you will be making TWO separate plots
Time (min)
0.0
1.0
5.0
10.0
20.0
30.0
40.0
N2O5 (M)
0.400
0.385
0.332
0.276
0.190
0.131
0.090
Make a plot (using Excel for example!! – NOT by hand!!) of the data as given. Plot Concentration of N2O5
vs. time (min). The overall reaction that you are examining is the decomposition of N2O5
2N2O5 (g)
→ 4NO2 (g) + O2 (g) at 85oC
Then take the data and re-plot except now you need to plot the data in order to generate the straight line
(direct relationship!). Make a new data table showing the data used for the plot that you are generating. Put
the equation for the line on the plot
a.) What is the k value?
b.) After 35 seconds, what would the concentration of N2O5 be?
12. For the reaction, A→ products, a graph of [A] vs. time gives a straight line. What is the order with
respect to A?
13. A mixture of hydrogen gas and oxygen gas is indefinitely stable at room temperature, however, if you
introduce a spark then BOOM!! What explanation can you offer for this observation? (HINT: heat is
NOT a catalyst!!)
14. Label the Ea values on the following energy diagram. Assume that the reactions are reversible so
make sure to label the energies as Ea forward and Ea reverse. Mathematically calculate the numerical
values of Ea forwards and Ea reverse!
Endothermic Reaction
30 kJ
energy
products E
a
12 kJ
5 kJ
Efinal
reactants
Ea forward
time
15. What is the MAJOR difference between an activated complex and an intermediate in a reaction?
16. Given the following reaction diagram below, label the transition state(s), the activation energy(ies),
the reactants, the products, and any intermediates that might be present. Label using the following
words/designations:
Energy
time