1. A friend argues that if mass were really conserved, he would never need to refill his gas tank. What explanation do you offer your friend?
The Law of Conservation of Mass does not apply to reactions involving combustion of matter.
The oil companies make gasoline in a way that it gets used up so that we are always required to replenish it.
The nucleii of the atoms (mass) of gasoline are converted into pure energy by the engine according to E = mc2.
The atoms (mass) of gasoline are rearranged and converted into exhaust fumes.
d. The atoms (mass) of gasoline are converted into exhaust fumes.

2. A refrigerator delays the spoilage of food by
killing microorganisms.
slowing the rate of chemical reactions within microorganisms.
expanding the water found within microorganisms.
diminishing the supply of oxygen to microorganisms.
B. slowing down the rate of chemical reactions within microorganisms.

3. Temperature

4. Why does wood burn slowly in air but rapidly bursts into flames when placed in pure oxygen?
There is a greater interaction between the wood and oxygen molecules.
Because oxygen can lower the activation energy of the reaction.
Pure oxygen reacts with carbon dioxide at a faster rate.
Fire is actually extinguished within pure oxygen.
A. There is a greater number of collisions between the wood and oxygen molecules.

5. Concentration

6. True or False? Catalysts increase the rate of a chemical reaction by increasing the activation energy required for a reaction to take place.
True
False

7. Catalysts Transformation of Ozone to Oxygen by Chlorine in atmosphere.
Ea is reduced by Chlorine catalyst.

8. If a reaction container feels cooler after a reaction has occurred, the reaction was
Endothermic
Exothermic

9. Ultraviolet Sun rays within the stratosphere cause oxygen molecules (O2) to transform into ozone molecules (O3). Is this an example of an exothermic or an endothermic reaction?
3 O UV  2 O3
Exothermic, because ultraviolet light is emitted.
Endothermic, because ultraviolet light is emitted.
Exothermic, because ultraviolet light is absorbed.
Endothermic, because ultraviolet light is absorbed.
D. Endothermic, because ultraviolet light is absorbed.

10. Energy and Chemical Reactions
Exothermic reaction: a chemical reaction that results in the net release of energy.
reactants products energy
Endothermic reaction: a chemical reaction in which there is a net consumption of energy.
energy reactants products

11. How is it possible to cause an endothermic reaction to proceed when the reaction causes energy to be less dispersed?
The reaction should be placed in a vacuum.
The reaction should be cooled down.
The concentration of the reactants should be increased.
The reaction should be heated.

12. What type of reactions tend to occur all by themselves without the continuous input of energy?
Exothermic reactions, because they increase entropy.
Endothermic reactions, because they increase entropy.
Exothermic reactions, because they decrease entropy.
Endothermic reactions, because they decrease entropy.
A. Exothermic reactions, because they increase entropy.

13. Energy and Chemical Reactions
Bond Energy:
Energy absorbed in order to break a chemical bond = energy released when the same chemical bond is formed.

14. How much energy must be absorbed during the chemical reaction in order to break the chemical bonds of the reactants?
H-H (bond energy: 436 kJ/mol)
Cl-Cl (bond energy: 243 kJ/mol)
H-Cl (bond energy: 431 kJ/mol)
H Cl2  2 HCl
862 kJ/mol
436 kJ/mol
679 kJ/mol
1,358 kJ/mol
431 kJ/mol

15. How much energy must be absorbed during the chemical reaction in order to break the chemical bonds of the reactants?
H Cl2  2 HCl
H-H (bond energy: 436 kJ/mol)
Cl-Cl (bond energy: 243 kJ/mol)
H-Cl (bond energy: 431 kJ/mol)
436 kJ/mol kJ/mol
+679 kJ/mol
A. Exothermic, with more than 50 kJ of energy released.

16. How much energy is released during the formation of the chemical bonds of the products?
H-H (bond energy: 436 kJ/mol)
Cl-Cl (bond energy: 243 kJ/mol)
H-Cl (bond energy: 431 kJ/mol)
H Cl2  2 HCl
862 kJ/mol
436 kJ/mol
679 kJ/mol
1,358 kJ/mol
431 kJ/mol

17. How much energy must be absorbed during the chemical reaction in order to break the chemical bonds of the reactants?
H Cl2  2 HCl
H-H (bond energy: 436 kJ/mol)
Cl-Cl (bond energy: 243 kJ/mol)
H-Cl (bond energy: 431 kJ/mol)
436 kJ/mol kJ/mol
431 kJ/mol kJ/mol
+679 kJ/mol
-862 kJ/mol
A. Exothermic, with more than 50 kJ of energy released.

18. Is the chemical reaction endothermic or exothermic?
H-H (bond energy: 436 kJ/mol)
Cl-Cl (bond energy: 243 kJ/mol)
H-Cl (bond energy: 431 kJ/mol)
H Cl2  2 HCl
436 kJ/mol kJ/mol
431 kJ/mol kJ/mol
+679 kJ/mol
-862 kJ/mol
Endothermic
Exothermic

19. Exothermic with 183 kJ/mol of energy released.
How much energy must be absorbed during the chemical reaction in order to break the chemical bonds of the reactants?
H Cl2  2 HCl
H-H (bond energy: 436 kJ/mol)
Cl-Cl (bond energy: 243 kJ/mol)
H-Cl (bond energy: 431 kJ/mol)
436 kJ/mol kJ/mol
431 kJ/mol kJ/mol
+679 kJ/mol
-862 kJ/mol
Exothermic with 183 kJ/mol of energy released.
A. Exothermic, with more than 50 kJ of energy released.