AnswersHS Physical Science A - CR Summer School 2026Lab: Rate of Chemical Reactions

Lab: Rate of Chemical Reactions — Unit test Answers

25 verified answers
1
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What best explains whether bromine (Br) or neon (Ne) is more likely to form a covalent bond?

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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.
2
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Which ionic compound is used as a building material?

A
salt
B
limestone
C
magnesium oxide
D
iron oxide
3

The release of a gas from a chemical reaction is very quick. A scientist wants to measure what is released, but in small increments. What would allow the scientist to change the rate of the reaction so the results could be measured?

A
an enzyme
B
an inhibitor
C
a depressant
D
an accelerator
4

"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.
5

In which reaction would the activation energy result in an endothermic reaction?

A
water freezing
B
an egg cooking
C
a candle burning
D
iron rusting
6

What does the octet rule state that explains why atoms bond?

A
An atom bonds to have eight valence electrons to become stable.
B
An atom bonds to lose eight valence electrons to become stable.
C
An atom bonds to have eight valence electrons to become unstable.
D
An atom bonds to lose eight valence electrons to become unstable.
7

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.
8

What are the products of the combustion of a hydrocarbon?

A
carbon and oxygen
B
carbon dioxide and water
C
carbon and hydrogen
D
carbon dioxide and hydrogen
9

Which is a advantage of using cellulose?

A
its being produced in large quantities allows for a low cost
B
its lack of biodegradability
C
its harm to landfills
D
its high cost to recycle
10

Which balances the equation Mg + O2 → MgO?

A
Mg + 2O2 → 4MgO
B
2Mg + 2O2 → 2MgO
C
2Mg + O2 → 2MgO
D
2Mg + 2O2 → 4MgO
11

What else is produced during the replacement reaction of silver nitrate and potassium sulfate?2AgNO3 + K2SO4 Ag2SO4 + ________

Question illustration
A
KNO3
B
2KNO3
C
K2
D
2AgNO3
12

Which are long chains formed by the process of polymerization?

A
subunits
B
ethylenes
C
monomers
D
DNA strands
13

Hydrochloric acid and sodium hydroxide can be combined to form sodium chloride and water. Which best explains the reaction?

A
The mass of sodium hydroxide will result in the same mass of sodium chloride.
B
The total mass of hydrochloric acid and sodium hydroxide will result in a lower total mass of sodium chloride and water.
C
The mass of hydrochloric acid will result in the same mass of sodium chloride.
D
The total mass of hydrochloric acid and sodium hydroxide will result in the same total mass of sodium chloride and water.
14

Which is most likely a covalent compound?

A
LiF
B
MgS
C
NH3
D
CaCl2
15

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.
16

Sal drew the electron dot diagram of an aluminum atom as shown.

Question illustration
A
He should add five more dots so that the atom obeys the octet rule.
B
He should add ten more dots so that all thirteen electrons are shown.
C
He should add a single dot below the symbol.
D
He should add one dot below and one dot to the left of the symbol.
17

Which natural polymer makes up paper?

A
starch
B
nylon
C
wool
D
rubber
18

The activation energy of a reaction going on its own is 20 kJ. If the reaction was treated with a catalyst, which would most likely represent the amount of energy needed to start a reaction?

A
15 kJ
B
20 kJ
C
25 kJ
D
30 kJ
19

Which statement best describes the diagram below?

Question illustration
A
The pressure is greater at the bottom of the container.
B
The pressure is greater at the top of the container.
C
The temperature is greater at the top of the container.
D
The temperature is greater at the bottom of the container.
20

Which refers to a macromolecule that forms as a result of the joining of multiple monomers?

A
amino acid
B
glucose
C
nucleic acid
D
polymer

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