CHAPTER 12 CHEMICAL KINETICS 1
CHAPTER 12 CHEMICAL KINETICS I
Exercises
Reaction Rates
23.Consider the reaction
4PH3(g) P4(g) + 6H2(g)
If, in a certain experiment, over a specific time period, 0.0048 mole of PH3 is consumed in a 2.0 l container each second of reaction, what are the rates of production of P4 and H2 in this experiment?
Rate = = mol/L•s
= = ______mol/L•s
= =______mol/L•s
25.At 40C, H2O2 (aq) will decompose according to the following reaction
2H2O2 (aq) 2H2O(l) + O2 (g)
Using the data from page 593
a.Calculate the average rate of decomposition of of H2O2 between 0 and 2.16 x 104 s. Use this rate to calculate the average rate of production of O2 (g) over the same time period
Average rate = = ______mol/L•s
From the coefficients in the balanced equation:
= ______mol/L•s
b. What are these rates for the time period 2.16 x 104s to 4.32 x 104 s ?
= ______mol/L•s
= = ______mol/L•s
Notice that as time goes on in a reaction, the average rate decreases.
27.What are the units for each of the following if the concentrations are expressed in moles per liter and the time in seconds?
a) rate of a chemical reaction: The units for rate are always mol/L•s.
b) rate constant for a zero order rate law
c) rate constant for a first-order rate law
d) rate constant for a second-order rate law
e) rate constant for a third order rate law
Rate Laws from Experimental Data: Initial Rates Method
29.The reaction
2NO(g) + Cl2(g) 2NOCl(g)
Was studied at – 10C. The following results were obtained where
Rate=
Look at data page 594
a)What is the rate law?
Rate = k[NO]x[Cl2]y. you are solving for x and y
Try to examine experiments where only one concentration changes at a time. The more variables that change, the harder it is to determine the orders. Also, these types of problems can usually be solved by inspection. In general, we will solve using a mathematical approach, but keep in mind that you probably can solve for the orders by simple inspection of the data.
b)What is the value of the rate constant?
Rate = k[NO]x[Cl2]y. you are solving for k
31.The decomposition of nitrosyl chloride was studied:
2NOCl(g)2NO(g) + Cl2(g)
The following data were obtained where
Rate=
Look at data on page 594
- What is the rate law
Rate = k[NOCl]n; using experiments two and three: again you are solving for n
b. Calculate the value of the rate constant ( solve for k)
k = ______cm3/molecules•s
- Calculate the value of the rate constant when concentrations are given in moles per liter. You will need to take your answer from b with the correct units and switch Liters per mole per sec
1 Liter = 1000cm3 1mol = 6.022 x 1023 molecules
33. The reaction
I-(aq) +OCl- (aq) IO- (aq) + Cl-
Was studied, and the following data were obtained
a.What is the rate law? Solve for x and y
Rate = k[I−]x[OCl−]y
b.calculate the value of the rate constant. Solve for (k) use the first experiment and x and y
Rate = k[I−]x[OCl−]y
c.Calculate the initial rate for an experiment where both I- and OCl- are initially present at 0.15 mol/L/ use the k found in (b)
35.The rate of the reaction between hemoglobin (Hb) and carbon monoxide (CO) was studied at 20C. The following data were collected with all concentration units in micro mol/L (A hemoglobin concentration of 2.21 micro mol/ liter is equal to 2.21 x 10-6 mol/L
µ=micro=1x 10-6
- Determine the orders of this reaction with respect to Hb and CO
Rate = k[Hb]x[CO]y look at the data on page 595 to find x and y. you can do this by visual inspection!
First compare the first two experiments to find x
Then using the second and third experiments you can find can find y
- Determine the rate law (you are not calculating at this point)
Rate = k[Hb]x[CO]y
- Calculate the value of the rate constant (k) use the first experiment
k = ______L/mol•s check out the units
- What would be the initial rate for an experiment with [Hb]0 = 3.36 mol/L and
[CO]= 2.40 mol/L (use your k from c)
Rate = k[Hb]x[CO]y