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Chem 116 - General Chemistry II

Kinetics: Reaction Rate and Rate Laws

Determining the Specific Rate Constant

Consider the theoretical reaction:  3 X  + Y + 2 Z ➞ Products.  Initial rate data is shown below. 

[X]

[Y]

[Z]

-d[X]/dt (M/s)
(or initial rate of consumption of reactant X)

0.0092 M

0.11 M

2.0 M

1.6×10–2

0.0092 M

0.11 M

1.0 M

1.6×10–2

0.0138 M

0.055 M

2.0 M

1.8×10–2

0.023 M

0.11 M

2.0 M

10.×10–2


What is the rate law for this reaction? 
What is the value of the specific rate constant for this reaction?

Video Solution

Kinetics of a First Order Reaction I

A certain first order reaction has a half-life of 106 minutes.  How many hours will it take for the reactant concentration to decrease to 2.00% of its original concentration?

Video Solution

Kinetics of a Zeroth Order Reaction

A certain zeroth order reaction has a half-life of 3.5 hours at an initial concentration of 0.450 M of reactant.  What concentration of reactant remains after 72 minutes?


Video Solution

Kinetics of a Second Order Reaction

A certain second order reaction has a specific rate constant of 0.0086 M-1s-1. If, after an elapsed time of 19 minutes the amount of reactant left is 0.100 M, how much reactant was present initially?

Video Solution

Kinetics of a First Order Reaction II

A certain first order reaction has a half-life of 1.6 minutes.  How long will it take for the reactant concentration to drop by 99.90%?

Video Solution

Percentage of Remaining Reactant after Six Half-Lives

What percentage of reactant A remains after six half-lives have elapsed?

For this reaction, as the reactant concentration A increases, the half-life for the reaction increases.  This reaction is _________ order in [A].


Video Solution

Kinetics of First Order Reaction III

At 1000C, cyclobutane (C4H8) decomposes to two molecules of ethylene (C2H4). The rate constant for this reaction is 87 s-1.

If the initial C4H8 concentration is 2.00 M, what is the concentration after 0.10 s?

C4H8 ➞ 2C2H4


Video Solution

Kinetics of First Order Reaction IV

Cyclopropane is the smallest cyclic hydrocarbon. Because its 60 degree bond angle allows poor orbital overlap, its bonds are weak. As a result, it is thermally unstable and rearranges to propene at 1000 C via a first order reaction. The rate constant is 92 s-1.

What is the half-life of the reaction?

 

How long does it take for the concentration of cyclopropane to reach one-quarter of the intial value?
Video Solution

Kinetics of First Order Reaction V

The decomposition of hydrogen peroxide in dilute sodium hydroxide solution is described by the equation:

2H2O2 (aq)➞ 2H2O (l) + O2 (g)

 

The reaction is first-order in H2O2, the specific rate constant for the consumption of H2O2 at 20 C is 1.8 X 10-5 s-1 and the intial concentration is 0.30 M

 

What is the half-life (in hours) of the reaction at 20 C?

 

What is the molarity of H2O2 after four half-lives?

 

How many hours will it take for the concentration to drop to 25 % of its original value?

 

What will be the concentration of the H2O2 after 555 minutes?
Video Solution

Kinetics of First Order Reaction VI

A reaction is first-order in the concentration of the reactant i.e. has a rate law: Rate = k[A]. This reaction has a half-life of 102 seconds.

 

What is the numerical value of k?

 

How much time (in minutes) will it take for 84.0 % of the reactant to react?

 

If 0.50 M of reactant is present intially, how much reactant would remain after 5 minutes?

 

After three half-lives, what percent of reactant will remain?
Video Solution

Kinetics of First Order Reaction VII

A specific rate constant for a certain first order reaction is 0.0447 hr-1. What is the half-life of the reaction?
Video Solution

Kinetics of First Order Reaction VIII

The active ingredient in any over the counter pain killer analgesic decomposes with a rate constant of k = 9.05 X 10-4 day-1. How many days does it take for 15 % of the ingredient to decompose?
Video Solution

Kinetics of First Order Reaction IX

The decomposition of SOCl2 is first-order in SOCl2. If the half-life of the reaction is 4.1 hr, how long would it take for the concentration of SOCl2 to drop from 0.36 M to 0.045 M?
Video Solution

Kinetics of Second Order Reaction II

At elevated temperatures, nitrogen dioxide decomposes to nitric oxide and molecular oxygen:

2NO2 (g)➞ 2NO (g) + O2 (g)

 

Concentration-time data for the decomposition of NO2 at 300 C is included.

 

From the prepared plots given determine the order of the reaction.

 

How can you determine the rate constant?

 

What is the concentration of NO2 at t = 20.0 min?

 

What is the half-life of the reaction when [NO2 ] = 6.00 X 10-3 M?

 

What is the half-life when [NO2] = 3.00 X 10-3 M?

 

How much time will it take for 25 % of NO2 to react when [NO2 ] = 8.00 X 10-3 M?
Video Solution

Kinetics of Second Order Reaction III

A certain reaction is known to be second order in A with k = 4.36 X 10-2 M-1 hr-1. What is the numerical value of the half-life when the initial concentration of A is 0.250 M?
Video Solution

Kinetics of Second Order Reaction IV

A certain reaction is known to be second order in A with k = 0.014 X M-1s-1. What will be the concentration of A after 3.0 hours if the initial concentration is 0.025 M?
Video Solution