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Chemistry 12 - Unit 3 Quiz



True/False
Indicate whether the sentence or statement is true or false.
 

1. 

A physical change usually involves a greater enthalpy change than does a chemical change.
 

2. 

In a potential energy diagram, the activated complex is at a maximum potential energy for the system.
 

3. 

The potential energy of the products is greater than the potential energy of the reactants in an exothermic change.
 

4. 

The standard enthalpy of formation of a substance is measured at 25°C and 100 kPa.
 

5. 

An exothermic reaction absorbs heat from the surroundings.
 

6. 

The overall order of reaction is the sum of the exponents in the rate law equation.
 

7. 

The activation energy is lower in a catalyzed reaction than in the same reaction without a catalyst.
 

8. 

All of a radioisotope will have decayed after two half-lives.
 

9. 

In an endothermic reaction, both the potential and kinetic energies of the chemical system increase.
 

10. 

Elementary steps usually involve one- or two-body collisions.
 

Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
 

11. 

Which of the following statements does not apply to the term “enthalpy”?
a.
It is symbolized by the letter H.
b.
It is the same for all substances.
c.
It changes during a chemical reaction.
d.
It increases during the formation of some substances.
e.
It is described as potential energy.
 

12. 

Which of the following statements is false concerning c12-u3_files/i0140000.jpgH?
a.
It is the difference between the potential energies of reactants and products.
b.
It represents a change in potential energy.
c.
If it is negative, it represents an endothermic reaction.
d.
If the reaction consumes heat, it is positive.
e.
It may be written as part of the equation.
 

13. 

When solid ammonium nitrate is added to water, the solution feels cold to the hand. Which statement best describes this observation?
a.
Heat is released from the system, so it feels colder.
b.
The reaction is exothermic.
c.
The potential energy of the surroundings has increased.
d.
NH4NO3(aq) c12-u3_files/i0150000.jpg NH4NO3(s)  +  31 kJ
e.
NH4NO3(s) c12-u3_files/i0150001.jpg NH4NO3(aq)      c12-u3_files/i0150002.jpgH  =  +131 kJ
 

14. 

The reaction that would release the least energy is:
a.
condensation of a mole of water vapour
b.
combustion of a mole of hydrogen
c.
breaking the chlorine–chlorine bonds in a mole of Cl2(g)
d.
nuclear fission in a mole of uranium
e.
melting a mole of ice
 

15. 

A student dissolves some sodium hydroxide in water in a process represented by the equation
NaOH(s) c12-u3_files/i0170000.jpg Na+(aq)  +  OH(aq)
      The following temperatures are recorded:
initial temperature of water = 19.0°C
final temperature of resulting solution = 27.0°C
      Based on these observations, which of the following statements is true?
a.
The dissolving of NaOH is endothermic.
b.
The kinetic energy of NaOH(s) is higher than the kinetic energy of the ions.
c.
The reaction has a positive c12-u3_files/i0170001.jpgH value.
d.
Heat is absorbed from the surroundings.
e.
The potential energy of NaOH(s) is higher than the potential energy of the ions.
 

16. 

Refer to the reaction below. How much heat is released if 95.0 g of sodium metal reacts?
2 Na(s)  +  2 H2O(l)  c12-u3_files/i0180000.jpg  H2(g)  +  2 NaOH(aq)  +  150 kJ
a.
155 kJ
b.
246 kJ
c.
310 kJ
d.
620 kJ
e.
734 kJ
 

17. 

Which of the following representations of enthalpy changes in chemical reactions is inconsistent with the rest?
a.
CH3OH(l)  +  O2(g)  c12-u3_files/i0190000.jpg  CO2(g)  +  2 H2O(g)       c12-u3_files/i0190001.jpgH = –638.0 kJ
b.
CH3OH(l)  +  O2(g) c12-u3_files/i0190002.jpg  CO2(g)  +  2 H2O(g)  c12-u3_files/i0190003.jpg  638.0 kJ
c.
CH3OH(l)  +  O2(g)  c12-u3_files/i0190004.jpg  CO2(g)  +  2 H2O(g)      c12-u3_files/i0190005.jpgH = –1276.0 kJ
d.
c12-u3_files/i0190006.jpgHc = –638.0 kJ/mol CH3OH
e.
CH3OH(l)  +  O2(g) –638.0 kJ  c12-u3_files/i0190007.jpg CO2(g)  +  2 H2O(g)
 

18. 

The term “chlorine” is used by people to mean a number of possible types of matter containing chlorine atoms, such as Cl2(g), Cl(g), and Cl(aq). Which of these forms of “chlorine” would have a zero standard enthalpy of formation?
a.
Cl2(g), Cl(g), and Cl(aq)
b.
Cl(g) only
c.
Cl(aq) only
d.
Cl2(g) only
e.
Cl2(g) or Cl(g)
 

19. 

Calculate the molar enthalpy of reaction per mole of carbon in the following reaction:
3 C(s)  +  2 Fe2O3(s)  + 466 kJ  c12-u3_files/i0210000.jpg 4 Fe(s)  +  3 CO2(g)
a.
+466 kJ/mol C
b.
+155 kJ/mol C
c.
+117 kJ/mol C
d.
–466 kJ/mol C
e.
–155 kJ/mol C
 

20. 

In which of the following combinations of reactants would surface area most affect rate of reaction?
a.
sodium chloride and silver nitrate solutions
b.
hydrogen and chlorine gases
c.
glucose and potassium permanganate solutions
d.
sodium hydroxide and hydrochloric acid solutions
e.
copper metal and aqueous nitric acid
 

21. 

Which of the following statements is false?
a.
A catalyst increases the rate of a chemical reaction.
b.
A catalyst is consumed in a chemical reaction.
c.
A catalyst can be either homogeneous or heterogeneous.
d.
A catalyst lowers the activation energy barrier for a reaction.
e.
A catalyst has no effect on the enthalpy change in the reaction.
 

22. 

At about 300K, an increase in temperature of 10°C roughly
a.
increases the rate of reaction by a factor of 2
b.
decreases the rate of reaction by a factor of 2
c.
increases the rate of reaction by a factor of 10
d.
increases the rate of reaction by a factor of 100
e.
increases the rate of reaction by a factor of 1/3
 

23. 

The value of k in the rate law equation for a chemical reaction is affected most by
a.
increasing the concentration of a reactant
b.
finely dividing particles of a reactant
c.
lowering the reaction temperature
d.
decreasing the partial pressure of a gaseous reactant
e.
removing the product as it is formed
 

24. 

For a hypothetical reaction with a rate law equation of rate = k[X]m[Y]n, the rate of the reaction over time will probably decrease due to
a.
a decrease in the value of k
b.
a decrease in the values of m and n
c.
a decrease in the values of [X] and [Y]
d.
all of the above
e.
the rate does not decrease
 

25. 

For the rate law equation rate  =  k[N2O5(g)], the initial rate of the reaction, r, is 2.20 c12-u3_files/i0270000.jpg 10-4 mol/(L·s) when [N2O5(g)] is 0.140 mol/L. The value of k for this reaction at this temperature is
a.
2.34  c12-u3_files/i0270001.jpg  10-4/s
b.
3.52  c12-u3_files/i0270002.jpg  10-3/s
c.
3.60  c12-u3_files/i0270003.jpg  10-2/s
d.
6.36  c12-u3_files/i0270004.jpg  10-1/s
e.
1.57  c12-u3_files/i0270005.jpg  10-3/s
 

26. 

The rate of a chemical reaction would be expected to increase the most if
a.
the activation energy doubled
b.
the concentration of reactants doubled
c.
the activation energy were halved
d.
the surface area were doubled
e.
the temperature were halved
 

27. 

If 1.0 g of copper reacts with excess nitric acid in 45 s, the average rate of reaction is
a.
c12-u3_files/i0290000.jpg mol/s
b.
c12-u3_files/i0290001.jpg mol/s
c.
c12-u3_files/i0290002.jpg mol/s
d.
c12-u3_files/i0290003.jpg mol/s
e.
45 c12-u3_files/i0290004.jpg 1.0 c12-u3_files/i0290005.jpg 63.55 mol/s
 

28. 

Which one of the following statements is not a significant part of the collision–reaction theory?
a.
motion of molecules
b.
orientation of molecules on collision
c.
kinetic energy of the molecules on collision
d.
enthalpy change of the reaction
e.
temperature dependence of molecule speed
 

29. 

Which of the following statements about an activated complex is not correct?
a.
The potential energy of the activated complex is greater than that for the reactants.
b.
The activated complex is more complex than the reactants.
c.
The activated complex is more stable than the reactants.
d.
The activated complex has a high potential energy.
e.
The potential energy of the activated complex is greater than that of the products.
 

30. 

Which of the following statements is true for a reaction mechanism?
a.
Any catalyst is consumed.
b.
Collisions involving three or more particles are common.
c.
All steps have the same activation energy.
d.
The overall rate depends on the slowest step.
e.
The total activation energy is the same for catalyzed and uncatalyzed mechanisms.
 



 
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