Answers2025-2026_MDCPS_2003345_Chemistry_1_A-CRUnit Test

Unit Test — Unit test Answers

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1
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Which of these scenarios is most likely a chemical reaction?

A
A gas turns into a liquid as it releases energy.
B
A liquid becomes a gas as it absorbs energy.
C
Two white solids are added to a colorless liquid, and a colorless liquid remains.
D
Two colorless liquids are added together, and a colorless liquid and a green solid remain.
2
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Which statement best characterizes chemical reactions?

A
They always occur very quickly.
B
Their rates vary significantly.
C
Their rates are always slow.
D
They rarely occur in the natural environment.
3

What is the word equation for atoms of magnesium reacting with molecules of oxygen to produce magnesium oxide?

A
magnesium + magnesium oxide oxygen
Option A
B
magnesium + oxygen magnesium oxide
Option B
C
magnesium oxide + oxygen magnesium
Option C
D
magnesium + oxygen magnesium + oxygen
Option D
4

Which symbol can be used to indicate a chemical reaction that takes place in the presence of a catalyst?

A
350 degrees Celsius over a right-pointing arrow.
Option A
B
Upper P t over a right-pointing arrow.
Option B
C
0.5 a t m over a right arrow.
Option C
D
Delta over a right arrow.
Option D
5

The equation shows lead reacting with sulfuric acid to produce lead sulfate and hydrogen gas.Which type of chemical reaction does this equation represent?

Question illustration
A
synthesis
B
decomposition
C
single replacement
D
double replacement
6

Error

Answer not available
7

What is the percent by mass of potassium in K3Fe(CN)6?Use .

Question illustration
A
16.96%
B
21.88%
C
25.53%
D
35.62%
8

Which reaction will most likely take place based on the activity series?Li > K > Ba > Ca > Na > Mn > Zn > Cr > Fe > Cd > Ni > H > Sb > Cu > Ag > Pd > Hg > Pt

A
Pt + FeCl3
Option A
B
Mn + CaO
Option B
C
Li + ZnCO3
Option C
D
Cu + 2KNO3
Option D
9

What is the percent by mass of oxygen in carbon dioxide (CO2)?Use .

Question illustration
A
27.29%
B
57.12%
C
72.71%
D
79.99%
10

Error

Answer not available
11

Consider the chemical equation for the combustion of sugar._C6H12O6(s) + _O2(g) _CO2(g) + _H2O(l)Which sequence of coefficients should be placed in the blanks to balance this equation?

Question illustration
A
1, 6, 6, 6
B
6, 1, 6, 1
C
3, 3, 3, 6
D
1, 3, 3, 6
12

This formula equation is unbalanced.Pb(NO3)2(aq) + Li2SO4(aq) PbSO4(s) + LiNO3(aq) Which coefficient should appear in front of LiNO3 in the balanced equation?

Question illustration
A
1
B
2
C
3
D
4
13

When two substances are mixed together, a color change is observed. Does this mean that a chemical reaction has definitely occurred?

A
Yes because any change indicates a chemical reaction.
B
No because some physical changes produce color changes.
C
No because color changes are not indicators of chemical reactions.
D
Yes because color changes occur only when new compounds are formed.
14

Which statement describes a chemical reaction?

A
Reactants form products when atoms change state.
B
Products form reactants when atoms change state.
C
Reactants form products when atoms are rearranged.
D
Products form reactants when atoms are rearranged.
15

Which characteristic best identifies a decomposition reaction?

A
a single compound as a reactant
B
a single compound as a product
C
an element and a compound as reactants
D
an element and a compound as products
16

Which type of reaction is represented by the generic equation AB + CD AD + CB?

Question illustration
A
combustion
B
decomposition
C
single replacement
D
double replacement
17

Which statement describes a chemical reaction?

A
Atoms in the products are rearranged to form new substances.
B
Atoms in the reactants are rearranged to form new substances.
C
Atoms in the products change into new atoms to form new substances.
D
Atoms in the reactants change into new atoms to form new substances.
18

What is the empirical formula for C2H6?

A
CH
B
CH3
C
C2H4
D
C6H18
19

A sample of a compound contains 60.0 g C and 5.05 g H. Its molar mass is 78.12 g/mol. What is the compound’s molecular formula?

A
CH
B
C2H2
C
C6H6
D
C6H
20

A solid is placed in a solution. Which observation most likely indicates that a chemical reaction has occurred?

A
The size of the solid has rapidly decreased.
B
The color of the solution has not changed.
C
The solid has bubbles forming on its surface.
D
The temperature of the solution stays the same.

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