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Chemistry 12 Unit 1
 Chemical kinetics is the study of the rates of chemical
reactions
eg:
4 Fe(s) + 3 O2(g)  2 Fe2O3(s)
Ca(s) + 2 H2O(l)  Ca(OH)2(s) + H2(g)
2 H2(g) + O2(g)  2 H2O(g)
1. Measuring Rates of Chemical Reactions
• The rate of any reaction is measured as the change
in some quantity per time.
• Try to use a quantity that is easy to monitor.
eg:
From the previous reactions you might use:
•
•
•
(what happens to the total mass of the system?)
eg:
If 2.0 g of rust is produced in 5.0 yr, what is the
rate of rust produced in g/d?
eg:
If 2.5 L of H2 is produced in 1.5 min, what is
the rate of H2 produced in mL/s?
eg:
In a particular reaction, the concentration of HCl
decreases from 1.00 M to 0.50 M in 3.0 min. What is the
rate of this reaction in terms of concentration change?
Practice Problem:
Sodium carbonate reacts with hydrochloric acid producing table
salt, water and a non-combustible gas.
The following data was obtained:
Time (s)
Volume of gas (mL)
5.0
12
10.0
25
15.0
37
20.0
49
25.0
60
30.0
68
a)
b)
c)
d)
e)
f)
Write the balanced chemical equation.
Calculate the rate of production of gas from 5 to 15 seconds.
Calculate the overall rate of gas production at 30 seconds.
Calculate c) in mol/min assuming the reaction took place at STP.
Calculate the mass of sodium carbonate used up after 30 s.
Calculate the rate of the consumption of HCl in moles per
second.
g) Try to explain why the reaction slows down slightly over time.