1. Kinetics sample problems
Columbia College
Chemistry 1B
2/22/2019

2. Introduction We have already covered the general ideas of kinetics.
Now lets look at the general problems you may be addressing in this section.
2/22/2019

3. Topic One – Initial rate data
1. Ammonium ion (NH4+) reacts with nitrite ion (NO2– ) according to the equation:
NH4+ + NO2– ® N2(g) + 2H2O(l)
The following initial rates of reaction have been measured for the given reactant concentrations.
Expt.# NH4+ (M) NO2 –(M) Rate (M/hr)
What is the rate law (rate equation) for this reaction?
2/22/2019

4. Topic Two – Integrated Rate Equations
For the reaction:
X + Y ® Z, the reaction rate is found to depend only upon the concentration of X. A plot of 1/X verses time gives a straight line.
What is the rate law for this reaction?
2/22/2019

5. Topic Two – Integrated Rate Equations
The graphs below all refer to the same reaction. What order is this reaction?
2/22/2019

6. Topic Three – Half Lives
Use the data below to calculate the half-life of acetaldehyde decomposition at 364 mmHg?
The thermal decomposition of acetaldehyde is a second-order reaction.
CH3CHO ® CH4 + CO
The following data points were obtained at 518°C.
The initial pressure of CH3CHO is 364 mm Hg.
time, s
P CH3CHO, mmHg 42
330
105
290
720
132
2/22/2019

7. Topic Four – Activation Energy
What is the slope of an Arrhenius plot for the following reaction?
2NOCl ® 2NO + Cl2
Temperature (K)
k (L mol –1 s –1)
400
6.6 X 10-4
500
2.9 X 10-1
600
16.3
2/22/2019

8. Topic Four – Activation Energy
The activation energy for the reaction 2HI ® H2 + I2 is 184 kJ/mol. How many times greater is the rate constant for this reaction at 520°C than at 500°C? R = 8.31 J/mol·K.
2/22/2019

9. Summary We have gone over 4 main types of problems in kinetics
There are more ways to approach these same ideas … forward and backwards.
2/22/2019