# Kinetics Worksheet – Reaction Rates and Rate Laws - PDF by PaulyDeacon

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```									Chem 128                                Dr. Abel                                                 1

Kinetics Worksheet – Reaction Rates and Rate Laws

1) What are the usual units of reaction rate?

2) Concentrations of trace gases in the atmosphere are sometimes expressed in
molecules/cm3. If these units are used for the concentrations, then what are the units for the
reaction rate?

3. The compound RX3 decomposes according to the equation

3RX3 → R + R2X3 + 3X2

In an experiment the following data were collected for the decomposition at 100°C. What is
the average rate of reaction over the entire experiment?

t(s)    [RX3](mol L-1)
0       0.85
2       0.67
6       0.41
8       0.33
12      0.20
14      0.16

4. Consider the following reaction

8A(g) + 5B(g) → 8C(g) + 6D(g)

If [C] is increasing at the rate of 4.0 mol L-1s-1, at what rate is [B] changing?

5. For the reaction

3A(g) + 2B(g) → 2C(g) + 2D(g)

the following data was collected at constant temperature. Determine the correct rate law for
this reaction.

Trial   Initial [A]   Initial [B]    Initial Rate
(mol/L)       (mol/L)        (mol/(L·min))
1       0.200         0.100          6.00 × 10-2
2       0.100         0.100          1.50 × 10-2
3       0.200         0.200          1.20 × 10-1
4       0.300         0.200          2.70 × 10-1
Chem 128                                Dr. Abel                                                   2
6. For the reaction

2A + B + 2C → D + E

the following initial rate data was collected at constant temperature. Determine the correct
rate law for this reaction. All units are arbitrary.

Trial       [A]           [B]           [C]           Rate
1           0.225         0.150         0.350         0.0217
2           0.320         0.150         0.350         0.0439
3           0.225         0.250         0.350         0.0362
4           0.225         0.150         0.600         0.01270

7) Consider the reaction of peroxydisulfate ion with iodine ion:
3I-(aq) + S2O8-2(aq)  I3-(aq) + 2SO4-2(aq)
At a particular temperature, the initial rate of disappearance of S2O8-2 varies with reactant
concentration as shown in the following table:

Experiment     [S2O8-2] (M)      [I-] (M)   Initial Rate (M/s)
1            0.023          0.048          6.8x10-6
2            0.054          0.048          1.6x10-5
3            0.054          0.019          6.3x10-6
(a) Determine the general rate law for the reaction.

(b) What is the value of the rate constant for this reaction?

(c) If the rate of disappearance of S2O8- as a function of time, -∆[ S2O8-2]/∆t, is 1.5x10-3
M/s for a particular time interval, what is the value of the rate of disappearance of I- as
a function of time, -∆[ I-]/∆t, for the same time interval?

(d) What is the rate of formation of SO4-2 during the time interval in (c), that is, what is
∆[ SO4-2]/∆t?

(e) What is the rate of disappearance of I- when [S2O8-2] = 0.075 M and [I-] = 0.060 M?
(HINT: Use the general rate law here)

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