Name ____________________________________________________ period ____________ date ______________
Chapter 2 Study Guide
Chemical Reactions
and the Law of Conservation of Mass
1. Which of the following is an example of a chemical
reaction?
(circle one)
a)
water boiling for tea
b)
chalk washing off of a driveway
c)
rock candy forming when water evaporates from sugar water
d)
jeans going white after bleach is spilled on them.
2. Please explain why you chose the answer you did in number 1.
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3. An example of a chemical change is _____. (circle one)
a. Fog condensing on the inside of car windows on a cold morning.
b. The glowing of an electric light.
c. Charcoal burning in a grill.
d. Food coloring changing the color of frosting.
4. Please explain why you chose the answer you did in number 3.
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Name ____________________________________________________ period ____________ date ______________
5. For each of the following reactions, please
1. Label the reactants and products.
2. Identify what type of reaction it is (synthesis, decomposition, single
replacement or double replacement) and,
3. Balance the reaction.
Balance and label
Type?
___I2+___H2___HI
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____Li + _____HCl  ___LiCl + ___H2
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___C3H8 + ___O2  ___CO2 + ___H2O
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Name ____________________________________________________ period ____________ date ______________
6. One of these chemical equations does not follow the law of conservation of
mass, while the other does follow the law. Please identify which
equation follows the law and which does not, explaining why and
making your knowledge of the law of conservation of mass clear.
Equation A
Equation B
Ag + N2  Ag3N
6Ag + N2  2Ag3N
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Name ____________________________________________________ period ____________ date ______________
Chapter 2 Study Guide
Chemical Reactions
and the Law of Conservation of Mass
KEY
1. Which of the following is an example of a chemical
reaction?
(circle one)
a)
water boiling for tea
b)
chalk washing off of a driveway
c)
rock candy forming when water evaporates from sugar water
d)
jeans going white after bleach is spilled on them.
2. Please explain why you chose the answer you did in number 1.
__When the jeans turn white, the color change indicates that it was a chemical
reaction. All the other options are physical changes.
3. An example of a chemical change is _____. (circle one)
a. Fog condensing on the inside of car windows on a cold morning.
b. The glowing of an electric light.
c. Charcoal burning in a grill.
d. Food coloring changing the color of frosting.
4. Please explain why you chose the answer you did in number 3.
Any time something burns, it is a chemical reaction. Fog condensing is simply
a state change, an electric light is only an energy transformation from
electrical energy to light energy, and food coloring wis only mixing with
frosting, not reaction with it.
Name ____________________________________________________ period ____________ date ______________
5. For each of the following reactions, please
1. Label the reactants and products.
2. Identify what type of reaction it is (synthesis, decomposition, single
replacement or double replacement) and,
3. Balance the reaction.
Balance and label
Type?
_____I2+______H2__2_HI
____Synthesis__
I=2
I=1 2
H= 2
H= 1 2
__2_Li + __2__HCl  __2__LiCl + ______H2
Li = 1 2
Li = 1 2
H=
H= 2
1 2
Cl = 1 2
__Single replacement___
Cl = 1 2
______C3H8 + __5__O2  ___3__CO2 + __4__H2O
___Decomposition_
C=
3
C=1 3
H=
8
H=2 8
O=
2 10
O = 3 4 10
Name ____________________________________________________ period ____________ date ______________
6. One of these chemical equations does not follow the law of conservation of
mass, while the other does follow the law. Please identify which
equation follows the law and which does not, explaining why and
making your knowledge of the law of conservation of mass clear.
Equation A
Equation B
Ag + N2  Ag3N
6Ag + N2  2Ag3N
The law of conservation of mass states that during any chemical reaction,
atoms are not gained or lost. No atoms are created and no atoms are lost, they
are only rearranged. Equation A does not follow the law of conservation of
mass. In equation A, there are 2 atoms of Nitrogen in the reactants before the
reaction, and in the products, there is only one atom of Nitrogen. This shows
an atom of Nitrogen being lost, or destroyed, which violates the law of
conversation of mass.
Equation B, since it has coefficients showing the correct amounts of each
chemical, does follow the law of conservation of mass. Each type of element
has the same number of atoms both before and after reaction B, 6 silver atoms
and 2 Nitrogen atoms.