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Chemistry - Chapter 7: Chemical Reactions


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

 1. 
A release of energy is a sign that
a.
a chemical change is taking place.
c.
oxygen is present.
b.
a physical change has just occurred.
d.
organic chemicals are present.
 

 2. 
Chemical energy is energy that is
a.
added to a reaction in the form of heat.
b.
stored in the form of chemical bonds.
c.
caused by the movement of electricity.
d.
released only when oxygen is present.
 

 3. 
What kind of reaction occurs when potassium is placed in water?
a.
a single-displacement reaction
c.
a decomposition reaction
b.
a double-displacement reaction
d.
electrolysis
 

 4. 
When methane reacts with abundant amounts of oxygen, the products are
a.
carbon dioxide and water.
c.
soot and water.
b.
carbon monoxide and water.
d.
simple sugar and oxygen.
 

 5. 
If you start with 5 mol of O2 in the reaction 2Mg + O2 ® 2MgO, how many moles of Mg will you need?
a.
4 mol
c.
8 mol
b.
5 mol
d.
10 mol
 

 6. 
All of the following factors may speed up a chemical reaction except
a.
smaller surface area.
c.
higher temperature.
b.
higher pressure.
d.
presence of a catalyst.
 

 7. 
Which of these is not a sign of a chemical reaction?
a.
A gas is given off.
c.
Heat is released.
b.
The material dissolves.
d.
A color change occurs.
 

 8. 
The substance that is formed in a chemical reaction is called the
a.
polymer.
c.
radical.
b.
reactant.
d.
product.
 

 9. 
Which of the following occurs in an endothermic reaction but not in an exothermic reaction?
a.
Chemical bonds are broken.
c.
Molecules are formed.
b.
Energy is absorbed.
d.
Atoms are rearranged.
 

 10. 
A type of reaction that produces an increase in temperature is
a.
endothermic.
c.
covalent.
b.
exothermic.
d.
nonpolar.
 

 11. 
An example of an endothermic reaction is
a.
bioluminescence by a firefly.
c.
burning gasoline.
b.
an exploding firecracker.
d.
photosynthesis by a plant.
 

 12. 
A reaction in which the products contain more chemical energy than the reactants is
a.
exothermic.
c.
endothermic.
b.
electrical.
d.
exergonic.
 

 13. 
Which of these represents the release of chemical energy?
a.
pouring gasoline into a tank
c.
a toy car running down a ramp
b.
burning charcoal in a grill
d.
warming food in a microwave
 

 14. 
Which of the following are the products and reactants of a chemical reaction most likely to have in common?
a.
atoms
c.
physical properties
b.
molecules
d.
chemical properties
 

 15. 
Which of the following occurs when gasoline is burned?
a.
New elements are formed.
c.
New molecules are formed.
b.
New atoms are formed.
d.
All of the above
 

 16. 
In a balanced chemical equation, the mass of the reactants is equal to the
a.
atoms in a molecule.
c.
volume of the reactants.
b.
atomic mass of the elements.
d.
mass of the products.
 

 17. 
What coefficient is missing in C2H4 + (?)O2 ® 2CO2 + 2H2O?
a.
2
c.
4
b.
3
d.
5
 

 18. 
Which of the following represents the word equation magnesium + oxygen ® magnesium oxide?
a.
CH4+ O2 ® CH4O2
c.
2Mg + O2 ® 2MgO
b.
MgO + O ® MgO2
d.
2CH4 + O2 ® 2CH3OH
 

 19. 
In the reaction 3CuCl2 + 2Al ® 2AlCl3 + 3Cu, how many moles of Al react with 3 moles of CuCl2?
a.
1 mol
c.
3 mol
b.
2 mol
d.
4 mol
 

 20. 
In the electrolysis of water, 2H2O ® 2H2 + O2, if the volume of oxygen produced was 8 mL, what would be the volume of hydrogen produced?
a.
4 mL
c.
16 mL
b.
8 mL
d.
24 mL
 

 21. 
If you use 3 mol of O2 in the reaction 2Mg + O2 ® 2MgO, how many moles of Mg are needed?
a.
1 mol
c.
4 mol
b.
2 mol
d.
6 mol
 

 22. 
Give the mole ratio for the following equation:
Zn + 2HCl ® ZnCl2 + H2.
a.
1:1:1
c.
1:2:1:1
b.
1:2:1
d.
1:2:2:2
 

 23. 
In the reaction 2H2O ® 2H2 + O2, if you start with 4 mol of water, how many moles of hydrogen gas are formed?
a.
2 mol
c.
6 mol
b.
4 mol
d.
8 mol
 

 24. 
Which of the following equations is not balanced?
a.
Fe + S ® FeS
c.
2Mg + O2 ® 2MgO
b.
KOH + HCl ® KCl + H2O
d.
NaCl + H2SO4 ® Na2SO4 + HCl
 

 25. 
The decomposition of water can be brought about by
a.
combustion.
c.
synthesis reactions.
b.
electrolysis.
d.
oxidation.
 

 26. 
Which of the following represents a double-displacement reaction between sodium chloride and silver fluoride?
a.
NaCl + AgF ® NaAgF + Cl2
c.
NaCl + AgF ® Ag + NaClF
b.
NaCl + AgF ® NaF + AgCl
d.
NaCl + AgF ® NaF + Cl2 + Ag
 

 27. 
A synthesis reaction between magnesium (Mg) and oxygen (O2) might produce
a.
Mg2.
c.
MgO.
b.
O4.
d.
MgCO2.
 

 28. 
At higher temperatures, food cooks faster because particles of food
a.
take up less space.
c.
collide more often.
b.
increase in number.
d.
come into contact with water.
 

 29. 
Catalysts that slow reactions are called
a.
inhibitors.
c.
balanced.
b.
substrates.
d.
endothermic.
 

 30. 
A slow reaction is likely to occur when the reactants have _____ temperatures and _____ surface areas.
a.
high, small
c.
high, large
b.
low, small
d.
low, large
 

 31. 
Which is not true of catalysts?
a.
They are used up in a reaction.
c.
They can slow down a reaction.
b.
They can speed up a reaction.
d.
They can be reused.
 

 32. 
Which is not true of enzymes?
a.
They are catalysts.
c.
They are affected by temperature.
b.
They are proteins.
d.
They are inefficient.
 

 33. 
When a chemical reaction and its reverse occur at the same time and rate, the reaction is said to be in
a.
equality.
c.
imbalance.
b.
equilibrium.
d.
redox.
 

 34. 
According to Le Châtelier’s principle, opening a soda can produce bubbles because which of the following changes occurs in the bottle?
a.
Pressure increases.
c.
Pressure decreases.
b.
Temperature increases.
d.
Temperature decreases.
 

 35. 
All of these are likely to speed up the rate of a reaction except
a.
decreasing the surface area.
c.
increasing the temperature.
b.
increasing the pressure.
d.
adding a catalyst.
 

 36. 
A substance that undergoes a change in a chemical reaction is
a.
a product.
c.
a reactant.
b.
a chemical.
d.
an enzyme.
 

 37. 
In an exothermic reaction, energy is transferred from
a.
the reactants to the surroundings.
c.
one reactant to another.
b.
the surroundings to the reactants.
d.
the container to the chemicals.
 

 38. 
The energy source in photosynthesis is
a.
light energy.
c.
heat energy.
b.
chemical energy.
d.
kinetic energy.
 

 39. 
A synthesis reaction is a reaction between at least two compounds in which
a.
one breaks down into at least two products.
b.
a compound is decomposed by an electric current.
c.
a compound burns in the presence of oxygen.
d.
a new, more complex compound is formed.
 

 40. 
The product of the synthesis reaction between sodium and chlorine gas is
a.
polyethylene.
c.
sodium chloride.
b.
carbon dioxide.
d.
copper(II) chloride.
 

 41. 
A chemical equation is balanced by changing or adding
a.
chemical symbols.
c.
coefficients.
b.
subscripts.
d.
reactants.
 

 42. 
In the reaction 2H2O ® 2H2 + O2, if you start with 2 mol of water, how many moles of hydrogen gas are produced?
a.
1 mol
c.
3 mol
b.
2 mol
d.
4 mol
 

 43. 
In the reaction H2S + 2O2 ® H2SO4, the law of definite proportions predicts that for every mole of H2S you will need how many moles of O2?
a.
1 mol
c.
3 mol
b.
2 mol
d.
4 mol
 

 44. 
In a balanced chemical reaction, the total mass of the products always equals the
a.
molar mass of the reactants.
c.
total mass of the reactants.
b.
atomic mass of the reactants.
d.
proportional masses of the reactants.
 

 45. 
Large, bulky molecules react more slowly than small ones because they have less opportunity to
a.
become heated.
c.
collide with other molecules.
b.
be mixed with catalysts.
d.
increase their surface area.
 

 46. 
What happens in a chemical reaction?
a.
Atoms are destroyed.
c.
Atoms are heated and cooled.
b.
Atoms are created.
d.
Atoms are rearranged.
 

 47. 
Which statement about endothermic reactions is correct?
a.
Energy is always created in the form of heat.
b.
Energy is transferred from the surroundings to the reactants.
c.
Energy is used to force electrons to move to higher energy levels.
d.
Energy is transferred from the reactants to the surroundings.
 

 48. 
Which of the following is an example of a decomposition reaction?
a.
photosynthesis
b.
digestion
c.
respiration
d.
exchange of ions between two compounds
 

 49. 
When water is broken down by electrolysis, the products are
a.
water and carbon dioxide.
c.
hydrogen gas and oxygen gas.
b.
hydrogen and oxygen ions.
d.
oxygen and methane.
 

 50. 
A balanced chemical equation shows the proportions of reactants and products necessary for
a.
the reaction to occur.
c.
energy use to be minimized.
b.
mass to be conserved.
d.
electrolysis to occur.
 

 51. 
In the reaction 2H2O2 ® 2H2O + O2, if you start with 4 mol of H2O2, how many moles of O2 will you end up with?
a.
4 mol
c.
2 mol
b.
3 mol
d.
1 mol
 

 52. 
A balanced chemical equation indicates both the number of particles of reactants and products and the number of
a.
orbits.
c.
nuclei.
b.
electrons.
d.
moles.
 

 53. 
What could you do to make yeast dough rise more slowly?
a.
Add more yeast to the mixture.
c.
Add mold spores to the dough.
b.
Knead the dough more vigorously.
d.
Reduce the temperature.
 

 54. 
An enzyme is a special kind of catalyst that works to
a.
speed up a specific biochemical reaction.
b.
slow down a chemical reaction.
c.
break down chemical elements.
d.
maintain the correct temperature for a reaction.