1. Rate of Reactions
Examples

2. 1.
The following reaction is observed: 2A + bB → cC + dD As the reaction progressed, the concentrations changed by these rates rateA = mol/L·s rateB = mol/L·s rateC = mol/L·s rateD = mol/L·s What are the values for the coefficients b, c, and d?

3. 2. For the oxidation of ammonia 4NH3 +3O2→2N2 +6H2O
it was found that the rate of formation of N2 was 0.27 mol L– 1 s–1.
At what rate was water being formed?
At what rate was ammonia being consumed?

4. 3.
Find the reaction rate of the decomposition of methane between 3 and 7 seconds.
Find the reaction rate of the production of oxygen gas between 2 and 6 seconds.
Identify the reactant and product based on the graph.

5. 4. The rate of a chemical reaction can be expressed in
energy released per mole of reactant
Grams per mole of reactant
moles per liter of solution
Volume of gas per minute

6. 5.
Consider the following reaction CaO (s) + 2 HCl (aq) → CaCl2 (aq) + H2O (l)
Which of the following could be used to measure the rate of the reaction?
Measure Δpressure/Δtime
Measure Δtotal mass/Δtime
Measure ΔpH/Δtime
Measure Δvolume/Δtime

7. 6. Consider the following reaction N2H4 (l)+2H2O2 (l)→N2 (g)+4H2O(l)
Which of the following could be used to determine the reaction rate in a closed system.
Measure the increase in gas pressure
Measure the decrease in gas pressure
measure the increase in mass of the system
Measure the decrease in mass of the system

8. 7.
Consider the following reaction N2H4 (l) + 2H2O2 (l) → N2 (g) + 4H2O(l)
In 55.0 sec, mole of H2O2 is consumed. The rate of production of N2 is
1.5x10-3 mole in 55s
0.33 mole per second
1.5 x 10-3 mole per second
0.006 mole per second

9. 8.
Which factor explains why lithium metal generally reacts faster than gold metal?
Concentration
Nature of the substance
Surface area
Temperature

10. 9. Consider the following reaction N2 (g)+2H2 (g) → 2NH3 (g)
The rate of formation of NH3 is g/s, the rate of consumption of N2 is
0.0765g/s
0.0306g/s
mole/s
mole/s

11. 10.
Nitrogen monoxide and hydrogen react according to the following reaction. 2NO(g) + 2H2 (g) → N2 (g) + 2H2O(g)
If the rate of hydrogen consumption is 0.87 g in 10 minutes, what is the rate of nitrogen production?
0.044g/min
0.61g in 10minutes
1.2 g/min
0.61g/min

12. 11. The iodate ion reacts with sulfite ions in the following reaction
IO3- (aq) + 3 SO32- (aq) → I- (aq) + 3 SO42- (aq)
Which of the following statements is true?
The disappearance of iodate is three times the disappearance of sulfite.
The disappearance of iodide is the same as the appearance of iodate.
The rate of formation of all the products are the same.
The rate of disappearance of sulfite is three times the disappearance of iodate.

13. 12.
For the reaction in question 11, what are the rates of iodide and sulfate ions being produced if the sulfite ion is disappearing at a rate of 2.4 x 10-4 mole/ Ls.
I- : 8.0 x 10-5 moles/L; SO42-: 2.7 X 10-5 moles/L
I- : 8.0 x 10-5 moles/L; SO42-: 2.4 X 10-4 moles/L
I- : 8.0 x 10-5 moles/s; SO42-: 2.4 X 10-4 moles/s
I- : 8.0 x 10-5 M/s; SO42-: 2.4 X 10-4 M/s

14. Answers

15. 1.
Step 1 - Find b rateB/rateA = b/coefficient of A b = coefficient of A x rateB/rateA b = 2 x 0.150/ b = 2 x 3 b = 6 For every 2 moles of A, 6 moles of B are needed to complete the reaction
Step 2 - Find c rateB/rateA = c/coefficient of A c = coefficient of A x rateC/rateA c = 2 x 0.075/ c = 2 x 1.5 c = 3 For every 2 moles of A, 3 moles of C are produced

16. Step 3 - Find d rateD/rateA = c/coefficient of A d = coefficient of A x rateD/rateA d = 2 x 0.025/ d = 2 x 0.5 d = 1 For every 2 moles of A, 1 mole of D is produced
The missing coefficients for the 2A + bB → cC + dD reaction are b=6, c=3, and d=1. The balanced equation is 2A + 6B → 3C + D

17. 2.
a) From the equation stoichiometry, Δ[H2O] = 6/2 Δ[N2], so the rate of formation of H2O is
3 × (0.27 mol L–1 s–1) = 0.81 mol L–1 s–1.
b) 4 moles of NH3 are consumed for every 2 moles of N2 formed, so the rate of disappearance of ammonia is
2 × (0.27 mol L–1 s–1) = 0.54 mol L–1 s–1.

18. 3.
Rate = 4.5 mL/s
Rate = 5.5 mL/s
Reactant: methane Product: oxygen

19. 4. The rate of a chemical reaction can be expressed in
energy released per mole of reactant
Grams per mole of reactant
moles per liter of solution
Volume of gas per minute

20. 5.
Consider the following reaction CaO (s) + 2 HCl (aq) → CaCl2 (aq) + H2O (l)
Which of the following could be used to measure the rate of the reaction?
Measure Δpressure/Δtime
Measure Δtotal mass/Δtime
Measure ΔpH/Δtime
Measure Δvolume/Δtime

21. 6. Consider the following reaction N2H4 (l)+2H2O2 (l)→N2 (g)+4H2O(l)
Which of the following could be used to determine the reaction rate in a closed system.
Measure the increase in gas pressure
Measure the decrease in gas pressure
measure the increase in mass of the system
Measure the decrease in mass of the system

22. 7.
Consider the following reaction N2H4 (l) + 2H2O2 (l) → N2 (g) + 4H2O(l)
In 55.0 sec, mole of H2O2 is consumed. The rate of production of N2 is
1.5x10-3 mole in 55s
0.33 mole per second
1.5 x 10-3 mole per second
0.006 mole per second

23. 8.
Which factor explains why lithium metal generally reacts faster than gold metal?
Concentration
Nature of the substance
Surface area
Temperature

24. 9. Consider the following reaction N2 (g)+2H2 (g) → 2NH3 (g)
The rate of formation of NH3 is g/s, the rate of consumption of N2 is
g/s
0.0306g/s
mole/s
mole/s

25. 10.
Nitrogen monoxide and hydrogen react according to the following reaction. 2NO(g) + 2H2 (g) → N2 (g) + 2H2O(g)
If the rate of hydrogen consumption is 0.87 g in 10 minutes, what is the rate of nitrogen production?
0.044g/min
0.61g in 10minutes
1.2 g/min
0.61g/min

26. 11. The iodate ion reacts with sulfite ions in the following reaction
IO3- (aq) + 3 SO32- (aq) → I- (aq) + 3 SO42- (aq)
Which of the following statements is true?
The disappearance of iodate is three times the disappearance of sulfite.
The disappearance of iodide is the same as the appearance of iodate.
The rate of formation of all the products are the same.
The rate of disappearance of sulfite is three times the disappearance of iodate.

27. 12.
For the reaction in question 11, what are the rates of iodide and sulfate ions being produced if the sulfite ion is disappearing at a rate of 2.4 x 10-4 mole/ Ls.
I- : 8.0 x 10-5 moles/L; SO42-: 2.7 X 10-5 moles/L
I- : 8.0 x 10-5 moles/L; SO42-: 2.4 X 10-4 moles/L
I- : 8.0 x 10-5 moles/s; SO42-: 2.4 X 10-4 moles/s
I- : 8.0 x 10-5 M/s; SO42-: 2.4 X 10-4 M/s