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Chapter 21 Chemical Reactions


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

 1. 
Which of the following statements describes a chemical change?
a.
A gas is given off when a liquid boils.
b.
A solid forms when a liquid freezes.
c.
A new substance is formed with different properties.
d.
A solid dissolves in a liquid.
 

 2. 
Which of the following occurs when water freezes?
a.
a physical change
c.
a chemical bond
b.
a chemical reaction
d.
a diatomic bond
 

 3. 
What is the force that holds two atoms together called?
a.
a chemical solution
c.
a chemical reaction
b.
a chemical mixture
d.
a chemical bond
 

 4. 
How do substances form during a chemical reaction?
a.
One or more substances are combined.
b.
Chemical bonds in molecules add atoms to make more molecules.
c.
A solid substance is formed in a solution.
d.
Chemical bonds break, atoms rearrange, and new chemical bonds form.
 

 5. 
A calcium carbonate molecule has 1 calcium (Ca) atom, 3 oxygen (O) atoms, and 1 carbon (C) atom. Which of the following shows the chemical formula for calcium carbonate?
a.
3CaCO
c.
CaCO3
b.
Ca2CO2
d.
CaC2O3
 

 6. 
The symbol for iron is Fe. The chemical symbol for oxygen is O. The formula for iron oxide, a type of rust, is Fe2O3. How many iron atoms are in one molecule of iron oxide?
a.
1
c.
3
b.
2
d.
4
 

 7. 
Which of the following is the product in the chemical formula N + O2 ® NO2?
a.
N
c.
O2
b.
O
d.
NO2
 

 8. 
Which of the following uses coefficients correctly to balance the equation
N2 + H2 ® NH3?
a.
N2 + 3H2 ® 2NH3
c.
N2 + H2 ® NH3
b.
2N2 + 2H2 ® 4NH3
d.
3N2 + 4H2 ® 6NH3
 

 9. 
Which of the following states the law of conservation of mass?
a.
Atoms are rearranged in a reaction and join new molecules.
b.
Compounds form a new compound with different properties.
c.
Mass cannot be created or destroyed in a chemical reaction.
d.
Energy is neither created nor destroyed in a chemical reaction.
 

 10. 
How many oxygen atoms are present in the reactant side of the chemical equation 4Fe + 3O2 ® 2Fe2O3?
a.
2
c.
4
b.
3
d.
6
 

 11. 
Which of the following equations shows a double-displacement
reaction?
a.
2Na + Cl2 ® 2NaC
c.
NaCl + AgF ® NaF + AgCl
b.
Zn + 2HCl ® ZnCl2 + H2
d.
H2CO3 ® H2O + CO2
 

 12. 
In a single-displacement reaction,
a.
a more reactive element can replace a less reactive element.
b.
only metals and nonmetals can react.
c.
a less reactive element can replace a more reactive element.
d.
most often nonmetals are involved.
 

 13. 
Which of the following is NOT an example of a chemical reaction?
a.
milk turning sour
c.
a match burning
b.
food being digested
d.
ice melting
 

 14. 
How many atoms are represented in the formula CaCO3?
a.
three
c.
five
b.
four
d.
six
 

 15. 
If a chemical symbol in a chemical formula has no subscript, it means
a.
the chemical symbol is written without any numbers.
b.
the element has no charge.
c.
the chemical is listed last in the formula.
d.
only one atom of the element is in the molecule.
 

 16. 
Which of the following is the chemical formula for a dinitrogen trioxide molecule?
a.
N2O3
c.
2N3O2
b.
3N2O
d.
NO3
 

 17. 
Which of the following examples shows where a coefficient is used correctly to balance the equation?
a.
Na + Cl2 ® 2NaCl
c.
2Na + Cl2 ® 2NaCl2
b.
Na + 2Cl2 ® 2NaCl
d.
2Na + Cl2 ® 2NaCl
 

 18. 
Which of the following is an example of a chemical reaction?
a.
a tire losing air
c.
a solid forming in solution
b.
water boiling
d.
ice melting
 

 19. 
Which of the following equations is an example of a single-displacement reaction?
a.
Fe + 2HCl ® FeCl2 + H2
c.
2H2O2 ® 2H2O + O2
b.
2Mg + O2 ® 2MgO
d.
NaOH + HCl ® NaCl + H2O
 

 20. 
How many atoms are represented in the formula CaCO3?
a.
three
c.
five
b.
four
d.
six
 

 21. 
What happens in an endothermic reaction?
a.
Energy is destroyed.
c.
Energy is created.
b.
Energy is released.
d.
Energy is taken in.
 

 22. 
Which of the following chemical reactions illustrates a decomposition reaction?
a.
2H2O ® 2H2 + O2
b.
4H2 + 2O2 ® 2H2O
c.
6CO2 + 6H2O + energy ® C6H12O6 + 6O2
d.
4KI + 2Cl2 ® 4KCl + 2I2
 

 23. 
Which of the following chemical reactions illustrates a synthesis reaction?
a.
2H2O ® 2H2 + O2
b.
4H2 + 2O2 ® 2H2O
c.
6CO2 + 6H2O + energy ® C6H12O6 + 6O2
d.
4KI + 2Cl2 ® 4KCl + 2I2
 

 24. 
Which of the following chemical reactions illustrates a single-displacement reaction?
a.
2H2O ® 2H2 + O2
b.
4H2 + 2O2 ® 2H2O
c.
6CO2 + 6H2O + energy ® C6H12O6 + 6O2
d.
4KI + 2Cl2 ® 4KCl + 2I2
 

 25. 
Which of the following chemical reactions illustrates an endothermic reaction?
a.
CaCO3 + energy ® CaO + CO2
b.
4H2 + 2O2 ® 2H2O
c.
6CO2 + 6H2O + energy ® C6H12O6 + 6O2
d.
4KI + 2Cl2 ® 4KCl + 2I2
 

 26. 
Which of the following is proof that a chemical reaction has taken place?
a.
A solid forms in a liquid.
b.
The color of a liquid changes.
c.
A new substance with different properties is formed.
d.
A substance becomes noticeably warmer.
 

 27. 
Substances that prevent chemical reactions are called_____.
a.
catalysts
b.
endothermics
c.
inhibitors
d.
products
e.
reactants
 

Completion
Complete each statement.
 

 28. 
A(n) ____________________ is used to balance chemical equations.
 

 

 29. 
The number that cannot change to balance a chemical equation is the ____________________.
 

 

 30. 
If an energy diagram shows products at a lower energy than the reactants, the diagram shows an ____________________ reaction.
 

 

 31. 
Energy released in exothermic reactions was first stored in chemical bonds in the ____________________.
 

 

Short Answer
 

 32. 
What is the difference between a reactant and a product?
 

 33. 
One element takes the place of another element in a compound. What kind of reaction is this?
 

 34. 
The following is the reaction for the explosion of nitroglycerin: What kind of reaction is this? 4C3H5(NO3)3 ® 12CO2 + 10H2O + 6N2 + O2
 

 35. 
What is the difference between a reactant and a catalyst?
 



 
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