AnswersEA ACADEMY PHYSICAL SCIENCE SPRINGUnit Test

Introduction to Chemical Reactions Answers

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How many atoms of each element are in the chemical formula Ca(OH)2?

A
1 calcium, 1 oxygen, and 1 hydrogen
B
1 calcium, 2 oxygen, and 2 hydrogen
C
2 calcium, 1 oxygen, and 2 hydrogen
D
2 calcium, 2 oxygen, and 2 hydrogen
2
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"Na2SO3” represents sodium sulfite.What does the 4 mean in the formula 4Na2SO3?

A
There are four atoms of sodium.
B
There are four atoms of sodium sulfite.
C
There are four molecules of sodium sulfite.
D
There are four elements in sodium sulfite.
3

Which is most likely a covalent compound?

A
LiF
B
MgS
C
NH3
D
CaCl2
4

To what extent do covalent compounds conduct electricity?

A
always
B
usually
C
rarely
D
never
5

Which is a characteristic of all ions?

A
They are metals.
B
They have a charge.
C
They are made of two or more types of atoms.
D
They form chemical bonds through electron sharing.
6

Which characteristic best distinguishes runoff and infiltration?

A
Runoff involves condensation and infiltration involves evaporation.
B
Runoff occurs over land and infiltration occurs underground.
C
Runoff occurs during floods and infiltration occurs during drought.
D
Runoff describes water movement and infiltration describes water storage.
7

Which statement about water best illustrates the property of adhesion?

A
water droplet found on a spider web in the morning
B
water molecules in a drop of dew
C
water is necessary for animal respiration
D
water dissolving salt into a solution
8

Which ionic compound is used as a building material?

A
salt
B
limestone
C
magnesium oxide
D
iron oxide
9

Which describes the substances that form covalent bonds?

A
a metal and a metalloid
B
a metal and a nonmetal
C
two nonmetals
D
two metals
10

Calcium carbonate (CaCO3) is a white solid with no odor. When CaCO3 is heated, the resulting substances are calcium oxide (CaO) and carbon dioxide (CO2). CaO is a white to gray solid with no odor, and CO2 is a gas with no odor and color.Which statement describes CaCO3?

A
It is a diatomic molecule that can’t be broken down by physical means.
B
It is a diatomic molecule that can’t be broken down by chemical means.
C
It is a compound that can be broken down by physical means.
D
It is a compound that can be broken down by chemical means.
11

What best explains whether bromine (Br) or neon (Ne) is more likely to form a covalent bond?

Question illustration
A
Bromine forms covalent bonds because it has seven valence electrons, but neon has eight valence electrons and already fulfills the octet rule.
B
Bromine forms covalent bonds because it has many electron shells, but neon has only two electron shells and is tightly bound to its electrons.
C
Neon forms covalent bonds because it can share its valence electrons, but bromine has seven valence electrons and can gain only one more electron.
D
Neon forms covalent bonds because it has only two electron shells, but bromine has many electron shells and will lose electrons in order to fulfill the octet rule.
12

Read the following excerpt about water availability to living organisms.“Water covers 75 percent of Earth. 97 percent of water on Earth is salt water. Only 3 percent of water is available as fresh water, but most of this water is locked up in solid glaciers and polar ice caps.” Based on this information, which is the best approximation of the amount of water on the planet that is available for animals to drink?

A
1 percent
B
3 percent
C
10 percent
D
75 percent
13

There are several different models that represent compounds. One type of model is shown.

Question illustration
A
a structural formula
B
a chemical formula
C
a space-filling model
D
a ball-and-stick model
14

Which sequence of processes transports water from the atmosphere to the ocean and then back into a cloud?

A
precipitation ® condensation ® transpiration
B
evaporation ® condensation ® sublimation
C
precipitation ® evaporation ® condensation
D
evaporation ® precipitation ® condensation
15

Shameeka is studying for an exam. She took the notes below about calcium and chlorine, which are known to form ionic bonds.Calcium, which is a metal, donates 2 electrons to chlorine.The individual calcium atoms become ions with a negative 2 charge. The bond between calcium and chlorine makes the atoms stable. Calcium and chlorine attract each other. Which best describes Shameeka’s error?

A
Calcium is a metal, so it donates protons, not electrons.
B
The individual calcium atom has a positive, not negative, 2 charge.
C
The bond formed makes the atoms unstable, not stable.
D
Calcium and chlorine repel, not attract, each other.
16

The table describes the properties of four compounds.Which compounds are most likely ionic?

Question illustration
A
compounds A and B
B
compounds B and C
C
compounds C and D
D
compounds D and A
17

What is formed when polyatomic ions bond with other ions?

A
ionic compounds
B
neutral compounds
C
ionic elements
D
neutral elements
18

Covalent bonds can be best described as

A
neutral atoms coming together to share electrons.
B
neutral atoms coming together to create electrons.
C
ionized atoms coming together to trade electrons.
D
ionized atoms coming together to destroy electrons.
19

After a covalent bond has stabilized an atom, the atom will have

A
fewer valence electron shells.
B
more valence electron shells.
C
an empty valence electron shell.
D
a full valence electron shell.
20

In carbon dioxide (CO2), there are two oxygen atoms for each carbon atom. Each oxygen atom forms a double bond with carbon, so the molecule contains two sets of double bonds.Two sets of double bonds means that the total number of electrons being shared in the molecule is

A
two.
B
four.
C
six.
D
eight.

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