Chemical Equations

1. In a chemical equation, the "+" symbol means:

A. is added to
B. is heated with
C. is reacted with
D. plus
E. none of the above

2. The law of conservation of mass states that:

A. matter never changes
B. matter can only be created not destroyed
C. mass can only be created not destroyed
D. mass cannot be created or destroyed
E. none of the above

3. Which of the following statements about skeleton equations is not true?

A. They are always properly balanced.
B. They have chemical symbols instead of words.
C. They indicate the molecules' physical state of matter.
D. They do not contain complete information.
E. None of the Above

4. Coefficients are:

A. subscripts placed after elemental symbols to indicate the phase of matter
B. superscripts placed after elemental symbols to indicate the phase of matter
C. superscripts placed before elemental symbols to indicate the quantity needed
D. numbers placed before elemental symbols to indicate the quantity needed
E. none of the above

5. Melting is a:

A. physical reaction
B. chemical reaction
C. reactant
D. product
E. none of the above

Synthesis

1. A synthesis reaction is also known as a:

A. creation reaction
B. replacement reaction
C. singular reaction
D. combination reaction
E. none of the above

2. In a combination reaction, how many products are formed?

A. One
B. Two
C. Three
D. Four
E. None of the Above

3. The most basic form of a synthesis reaction is:

A. A + B → C + D
B. A → B
C. A + B → AB
D. AB → A + B
E. None of the Above

4. Which of the following is not a combination reaction?

A. C (s) + O₂ (g) → CO₂ (g)
B. 2 C (s) + O₂ (g) → 2 CO (g)
C. SO₃ (g) + H₂O (l) → H₂SO₄ (aq)
D. NH₄NH₃ (s) → N₂O (g) + 2 H₂O (g)
E. None of the Above

5. Which type of synthesis reactions are rare?

A. Reactions involving four or more reactants
B. Reactions involving two or more reactants
C. Reactions done at 0ºC
D. Reactions done at room temperature
E. None of the Above

Decomposition

1. The most basic form of a decomposition reaction is:

A. A + B → C + D
B. A → B
C. A + B → AB
D. AB → A + B
E. None of the Above

2. The opposite of a decomposition reaction is a:

A. synthesis reaction
B. composition reaction
C. replacement reaction
D. combustion reaction
E. none of the above

3. Which is a form of energy that cannot initiate a decomposition reaction?

A. Heat
B. Shock
C. Electrolysis
D. Freezing
E. None of the Above

4. The method of applying a direct electrical current to facilitate a decomposition process, such as breaking down a water molecule, is called:

A. electrolysis
B. electro processes
C. electricity
D. lightning
E. none of the above

5. The "splitting" of water results in the formation of:

A. hydrogen peroxide
B. hydrogen and oxygen
C. hydrochloric acid
D. hydrogen and hydrogen peroxide
E. none of the above

Displacement

1. The most basic form of a single displacement reaction is:

A. A + B → C + D
B. A → B
C. AB + C → AC + B
D. AB + CD → AC + BD
E. None of the Above

2. The most basic form of a double displacement reaction is:

A. A + B → C + D
B. A → B
C. AB + C → AC + B
D. AB + CD → AC + BD
E. None of the Above

3. A double displacement reaction is also called a:

A. metathesis reaction
B. switcheroo reaction
C. combustion reaction
D. great exchange reaction
E. none of the above

4. When alkali metals react with water, what is produced?

A. MOH and H₂ (where M stands for a metal)
B. H⁺ and OH^-C. MO and H₂ (where M stands for a metal)
D. No reaction occurs
E. None of the Above

5. When a reaction releases heat, it is called:

A. spontaneous
B. aqueous
C. exothermic
D. endothermic
E. None of the Above

Combustion

1. The most basic form of a combustion reaction is:

A. hydrocarbon + oxygen → carbon dioxide + water
B. hydrocarbon + water → carbon dioxide + oxygen
C. hydrocarbon + carbon dioxide → water + oxygen
D. carbon dioxide + water → hydrocarbon + oxygen
E. none of the above

2. Combustion reactions produce:

A. heat and light
B. heat
C. light
D. odor
E. none of the above

3. A combustion reaction stops when it is deprived of:

A. carbon dioxide
B. water
C. oxygen
D. heat
E. none of the above

4. The products of combustion reactions are always:

A. carbon dioxide and water
B. hydrocarbon and oxygen
C. carbon dioxide and oxygen
D. hydrocarbon and water
E. none of the above

5. Combustion reactions are:

A. endothermic
B. exothermic
C. always slow
D. always fast
E. none of the above

Solutions

Chemical Equations

1. In a chemical equation, the "+" symbol means:
C. is reacted with
In a chemical equation the "+" symbol means is reacted with, while the "→" symbol means "to yield."

2. The law of conservation of mass states that:
D. mass cannot be created or destroyed
Law of Conservation of Mass states that in any chemical reaction, the mass of the products is always equal to the mass of the reactants. In other words, matter cannot be created or destroyed.

3. Which of the following statements about skeleton equations is not true?
A. They are always properly balanced.
A skeleton equation shows what the reactants and products are, but does not address what quantity of reacts and products are required. Therefore, skeleton equations are not always properly balanced.

4. Coefficients are:
D. numbers placed before elemental symbols to indicate the quantity needed
Coefficients are used to properly balance chemical equations. They are numbers placed before elemental symbols to indicate the quantity of reactant or product present. Unlike subscripts, these numbers can be altered to properly balance an equation.

5. Melting is a:
A. physical reaction
Any change of state (melting, freezing, and so on) is a form of physical change or physical reaction. There is no change in chemical identity so there is no chemical reaction.

Synthesis

1. A synthesis reaction is also known as a:
D. combination reaction
A synthesis reaction is also known as a combination reaction because two or more elements (or compounds) combine to form a new compound.

2. In a combination reaction, how many products are formed?
A. One
In a synthesis reaction two or more elements (or compounds) react to from a single product.

3. The most basic form of a synthesis reaction is:
C. A + B → AB
In a synthesis reaction two or more elements (or compounds) which are labeled as A + B combine to form a new compound, which is labeled as AB.

4. Which of the following is not a combination reaction?
D. NH₄NH₃ (s) → N₂O (g) + 2 H₂O (g)
All of the reactions follow the pattern A + B → AB except reaction D, in which one reactant forms two products.

5. Which type of synthesis reactions are rare?
A. Reactions involving four or more reactants
Synthesis reactions involving four or more reactants are extremely rare.

Decomposition

1. The most basic form of a decomposition reaction is:
D. AB → A + B
In a decomposition reaction a single compound which is labeled as AB breaks apart to form two or more new compounds or elements which are labeled as A + B.

2. The opposite of a decomposition reaction is a:
A. synthesis reaction
The opposite of a decomposition reaction is a synthesis or combination reaction.

3. Which is a form of energy that cannot initiate a decomposition reaction?
D. Freezing
Decomposition reactions involve the breaking of bonds so they require energy, which can be in the form of heat, electrolysis, or even shock from a small bump!

4. The method of applying a direct electrical current to facilitate a decomposition process, such as breaking down a water molecule, is called:
A. electrolysis
Electrolysis, by definition, is the method of applying a direct electrical current to a process.

5. The "splitting" of water results in the formation of:
B. hydrogen and oxygen
The splitting of water is the decomposition of water by electrolysis. The results of the decomposition are oxygen and hydrogen.

Displacement

1. The most basic form of a single displacement reaction is:
C. AB + C → AC + B
In a single displacement reaction a more active element displaces a less active element from a compound. This can be expressed by the general form of AB + C → AC + B.

2. The most basic form of a double displacement reaction is:
D. AB + CD → AC + BD<BR>In a double displacement reaction a switcheroo takes place. Two elements from two different compounds switch places. This can be expressed by the general form of AB + CD → AC + BD.

3. A double displacement reaction is also called a:
A. metathesis reaction
A double displacement reaction is also called a metathesis reaction. Scientists working this field were the recipients of the 2005 Nobel Prize in Chemistry.

4. When alkali metals react with water, what is produced?
A. MOH and H₂ (where M stands for a metal)
When an alkali metal such as sodium is reacted with water, hydrogen is displaced and NaOH is produced.
2 Na (s) + 2 H₂O (l) → 2 NaOH (aq) + H₂ (g)

5. When a reaction releases heat, it is called:
C. exothermic
An exothermic reaction releases heat, while an endothermic reaction absorbs heat.

Combustion

1. The most basic form of a combustion reaction is:
A. hydrocarbon + oxygen → carbon dioxide + water
The most basic form of a combustion reaction is:
 
hydrocarbon + oxygen → carbon dioxide + water
 
An example would be:
 
CH₄ + 2 O₂ → CO₂ + 2 H₂O

2. Combustion reactions produce:
A. heat and light
Combustion reactions produce heat and light, which is why they are a great way to run cars and heat our homes.

3. A combustion reaction stops when it is deprived of:
C. oxygen
A combustion reaction stops when it is deprived of oxygen. For example, when you put a glass jar over a burning candle the candle will stop burning once all of the oxygen is consumed.

4. The products of combustion reactions are always:
A. carbon dioxide and water 
hydrocarbon + oxygen → carbon dioxide + water
 
An example would be:
 
CH₄ + 2 O₂ → CO₂ + 2 H₂O

5. Combustion reactions are:
B. exothermic
Combustion reactions are generally fast reactions but not always. They are, however, always exothermic, which means they release heat.