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

Lab: Rate of Chemical Reactions — Unit test Answers

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1
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Shiloh wanted to observe the changes that occurred during an exothermic reaction. He monitored the changes and placed them in a chart. Which statement best describes his data?

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A
The activation energy was reached at 10:45 a.m. Without the additional energy, the reaction would have stopped.
B
The activation energy was reached at 11:15 a.m. The previous change was the threshold point for a reaction.
C
The activation energy was reached at 10:15 a.m. The additional energy allowed for a lower activity level.
D
The activation energy was reached was 10:45 a.m. The additional energy did not affect the reaction.
2
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What else is produced during the replacement reaction of magnesium and hydrochloric acid?Mg + 2HCl H2 + ________

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A
MgCl2
B
Mg2Cl2
C
Mg2Cl
D
MgCl
3

What does the chemical formula C3H6O2 tell about a molecule of the compound it represents?

A
It is made up of 3 atoms of 11 different elements.
B
It is made up of 11 atoms joined in a straight line.
C
It is made up of 11 total atoms of 3 different elements.
D
It is made up of 1 atom composed of 3 different elements.
4

Suna passes an electric current through a sample of clear, colorless, and odorless liquid. As the experiment continues, bubbles form, and the volume of liquid decreases. Suna collects samples of two colorless, odorless gases that bubble out of the liquid. One of the gases burns. Neither the original liquid nor the other gas burns.Which is the best explanation of her results?

A
The electric current changed some of the sample to gas even though the sample was not breaking down. Therefore, the original liquid is a compound.
B
The electric current released a gas that was odorless and colorless, like the original sample. Therefore, the original liquid is an element.
C
The sample was broken down by the electric current and formed a new substance that could burn. Therefore, the original liquid is a compound.
D
The sample lost some of its volume, but the gas still had the same chemical makeup as the original sample. Therefore, the original liquid is an element.
5

Formaldehyde is an organic compound. Each molecule includes two hydrogen (H) atoms, one oxygen (O) atom, and one carbon (C) atom. Below are the dot structures for each of these elements.Which diagram shows how the covalent bonds most likely form in a formaldehyde molecule?

Question illustration
A
Option
B
Option
C
Option
D
Option
6

Which represents an endothermic reaction?

A
wood burning in a fire
B
splitting a gas molecule
C
using a heat pack on an injury
D
TNT exploding
7

Which statement best describes the difference between endothermic and exothermic reactions?

A
They are opposites because endothermic reactions require energy and exothermic reactions release energy.
B
They are opposites because endothermic reactions release energy and exothermic reactions require energy.
C
They the same because they are both ways of forming precipitates.
D
They the same because they are both ways of forming gasses.
8

The first chart shows the effect of the normal breakdown of material from reactants to products. The second chart shows the same reaction but with an added modification.

Question illustration
A
Reaction A has an enzyme.
B
Reaction B has an enzyme.
C
Reaction A has an inhibitor.
D
Reaction B has an inhibitor.
9

If a chemical reaction does not reach its activation energy, which will most likely occur?

A
The chemical bonds will remain unchanged.
B
The chemical bonds will break.
C
The chemical bonds will have high kinetic energy.
D
The chemical bonds will already be broken.
10

What is produced during the replacement reaction of Cu(NO3)2 and Zn?

A
ZnNO3 + Cu
B
Zn + Cu(NO3)2
C
ZnCu + 2NO3
D
Zn(NO3)2 + Cu
11

The element sulfur (S) is most likely to form covalent bonds with the element

A
helium (He).
B
magnesium (Mg).
C
zinc (Zn).
D
oxygen (O).
12

Which is the only element in group 1 on the periodic table that forms covalent bonds?

A
hydrogen
B
lithium
C
potassium
D
sodium
13

What is a limitation of using a chemical formula, such as C6H12O6, to represent a compound?

T
The chemical formula does not show the types of elements that make up the compound.
T
The chemical formula does not show how the atoms are connected to one another.
T
The chemical formula does not show the number of atoms of each element in a molecule.
T
The chemical formula does not show the chemical symbols of the elements in the compound.
14

Which type of reaction is Mg + S → MgS?

p
polymerization
s
synthesis
r
replacement
d
decomposition
15

How many atoms of each element are in the chemical formula NH4NO3?

A
1 nitrogen, 1 hydrogen, and 3 oxygen
B
1 nitrogen, 4 hydrogen, and 3 oxygen
C
2 nitrogen, 4 hydrogen, and 3 oxygen
D
5 nitrogen, 1 hydrogen, and 1 oxygen

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