Chapter 4-Chemical Dominoes
Section 2: Balancing Chemical Equations
Post-Test
1) In the diagrams below, sulfur atoms are represented by gray circles
represented by black circles
, carbon atoms are
, and oxygen atoms are represented by white circles
.
Which of the following could be a product of the chemical reaction between sulfur and
oxygen?
a.
b.
c.
d.
2) A reaction occurs between two liquid substances in a sealed jar. What will happen to the
mass of the sealed jar and its contents after the reaction occurs?
a. The mass will change if a gas is formed, and it will change if a solid is formed.
b. The mass will change if a gas is formed, but it will not change if a solid is formed.
c. The mass will change if a solid is formed, but it will not change if a gas is formed.
d. The mass will not change if a gas is formed, and it will not change if a solid is
formed.
3) A student places some baking soda and a jar of lemon juice in a plastic bag and seals the
bag. She weighs the bag and everything in it. She shakes the bag so that the lemon juice
spills out of the jar and mixes with the baking soda inside the bag. The student observes
that bubbles form and the bag expands.
If the student weighs the bag and everything in it after the bubbling stops and compares
the final weight to the starting weight, what will she find out?
a. The final weight will be greater than the starting weight because new atoms are
produced during the experiment.
b. The final weight will be less than the starting weight because some of the atoms are
destroyed during the experiment.
c. The final weight will be the same as the starting weight because the number of each
kind of atom does not change during the experiment.
d. The final weight will be the same as the starting weight because some atoms are
destroyed, but new ones are created during the experiment.
4) When heated, oxygen reacts with copper to form copper oxide.
If this reaction occurs in a sealed container, will the mass of the container and everything
in it increase, decrease, or stay the same and why?
a. The mass will stay the same because the number of each kind of atom stays the same.
b. The mass will decrease because two substances combine to form one substance.
c. The mass will increase because a new kind of molecule is formed.
d. More information is needed to tell if the mass will change.
5) In the diagrams below, atoms are represented by circles, and molecules are represented
by circles that are connected to each other. The different colored circles represent
different kinds of atoms.
A propane molecule is made up of 3 carbon atoms and 8 hydrogen atoms. An oxygen
molecule is made up of 2 oxygen atoms.
This diagram shows one propane molecule and five oxygen molecules.
Which of the following diagrams could represent the molecules formed when propane
and oxygen molecules react?
Chapter 4-Chemical Dominoes
Section 2: Balancing Chemical Equations
Post-Test Answer Key
1)
2)
3)
4)
5)
B
D
C
A
C