CHEM 104 MODULE 2 – QUESTIONS AND
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1. Which quantity represents one mole of any substance?
A. 6.022 × 10²¹ particles
B. 6.022 × 10²² particles
C. 6.022 × 10²³ particles
D. 6.022 × 10²⁴ particles
: One mole contains 6.022 × 10²³ representative particles, a value known as
Avogadro's number. This relationship is fundamental to mole calculations in
chemistry.
2. A chemist calculates the molar mass of carbon dioxide (CO₂). Which value
is closest to its molar mass?
A. 28.01 g/mol
B. 32.00 g/mol
C. 44.01 g/mol
D. 60.01 g/mol
: Carbon contributes approximately 12.01 g/mol and two oxygen atoms
contribute approximately 32.00 g/mol, giving a total molar mass of about 44.01
g/mol.
3. A laboratory sample contains 2.0 moles of sodium chloride. Approximately
how many formula units are present?
,A. 3.01 × 10²³
B. 6.02 × 10²³
C. 1.20 × 10²⁴
D. 2.40 × 10²⁴
: Multiply the number of moles by Avogadro's number: 2.0 × 6.022 × 10²³ =
approximately 1.20 × 10²⁴ formula units.
4. Which conversion factor is used to convert grams of a substance into
moles?
A. Density
B. Molar mass
C. Volume
D. Atomic number
: The molar mass (g/mol) serves as the conversion factor between grams and
moles of a substance.
5. What is the molar mass of water (H₂O)?
A. 16.00 g/mol
B. 18.02 g/mol
C. 20.02 g/mol
D. 34.02 g/mol
: Water contains two hydrogen atoms (approximately 2.02 g/mol) and one
oxygen atom (approximately 16.00 g/mol), totaling about 18.02 g/mol.
6. Which statement best describes a mole?
A. A measure of temperature
B. A unit used to express the amount of substance
C. A unit of pressure
D. A measure of solution concentration
,: The mole is the SI base unit for the amount of substance and is widely used to
relate particles to measurable quantities such as mass.
7. Which quantity is required to calculate the empirical formula of a
compound?
A. Color of the compound
B. Percentage composition by mass of each element
C. Melting point only
D. Density only
: Empirical formulas are determined from the simplest whole-number mole ratio
of elements, which is calculated using percent composition data.
8. A chemist determines that a compound contains carbon and hydrogen in a
1:2 mole ratio. What is its empirical formula?
A. CH
B. CH₂
C. C₂H
D. C₂H₂
: The empirical formula represents the simplest whole-number ratio of atoms. A
1:2 ratio corresponds to CH₂.
9. Which law forms the basis for balancing chemical equations?
A. Boyle's Law
B. Charles's Law
C. Law of Conservation of Mass
D. Law of Multiple Proportions
: Chemical equations are balanced so that the number of atoms of each element
is conserved, consistent with the Law of Conservation of Mass.
, 10. Which coefficient correctly balances the oxygen molecule in the equation
below?
__H₂ + O₂ → __H₂O
A. 1
B. 2
C. 3
D. 4
: The balanced equation is 2H₂ + O₂ → 2H₂O. Therefore, the coefficient of O₂ is
1.
11. What is the coefficient of H₂ in the balanced equation below?
__H₂ + O₂ → __H₂O
A. 1
B. 2
C. 3
D. 4
: Two molecules of hydrogen react with one molecule of oxygen to produce two
molecules of water, balancing both hydrogen and oxygen atoms.
12. Which statement best describes a reactant?
A. A substance produced during a chemical reaction
B. A substance consumed during a chemical reaction
C. A catalyst used in a reaction
D. An experimental variable
: Reactants are the starting materials that undergo chemical change to form
products during a reaction.
ANSWERS | VERIFIED AND WELL DETAILED
ANSWERS PLUS S | GUARANTEED PASS |
LATEST EXAM UPDATE | EXAM PREP | STUDY
GUIDE | PRACTICE TEST | DOWNLOAD
INSTANT PDF
1. Which quantity represents one mole of any substance?
A. 6.022 × 10²¹ particles
B. 6.022 × 10²² particles
C. 6.022 × 10²³ particles
D. 6.022 × 10²⁴ particles
: One mole contains 6.022 × 10²³ representative particles, a value known as
Avogadro's number. This relationship is fundamental to mole calculations in
chemistry.
2. A chemist calculates the molar mass of carbon dioxide (CO₂). Which value
is closest to its molar mass?
A. 28.01 g/mol
B. 32.00 g/mol
C. 44.01 g/mol
D. 60.01 g/mol
: Carbon contributes approximately 12.01 g/mol and two oxygen atoms
contribute approximately 32.00 g/mol, giving a total molar mass of about 44.01
g/mol.
3. A laboratory sample contains 2.0 moles of sodium chloride. Approximately
how many formula units are present?
,A. 3.01 × 10²³
B. 6.02 × 10²³
C. 1.20 × 10²⁴
D. 2.40 × 10²⁴
: Multiply the number of moles by Avogadro's number: 2.0 × 6.022 × 10²³ =
approximately 1.20 × 10²⁴ formula units.
4. Which conversion factor is used to convert grams of a substance into
moles?
A. Density
B. Molar mass
C. Volume
D. Atomic number
: The molar mass (g/mol) serves as the conversion factor between grams and
moles of a substance.
5. What is the molar mass of water (H₂O)?
A. 16.00 g/mol
B. 18.02 g/mol
C. 20.02 g/mol
D. 34.02 g/mol
: Water contains two hydrogen atoms (approximately 2.02 g/mol) and one
oxygen atom (approximately 16.00 g/mol), totaling about 18.02 g/mol.
6. Which statement best describes a mole?
A. A measure of temperature
B. A unit used to express the amount of substance
C. A unit of pressure
D. A measure of solution concentration
,: The mole is the SI base unit for the amount of substance and is widely used to
relate particles to measurable quantities such as mass.
7. Which quantity is required to calculate the empirical formula of a
compound?
A. Color of the compound
B. Percentage composition by mass of each element
C. Melting point only
D. Density only
: Empirical formulas are determined from the simplest whole-number mole ratio
of elements, which is calculated using percent composition data.
8. A chemist determines that a compound contains carbon and hydrogen in a
1:2 mole ratio. What is its empirical formula?
A. CH
B. CH₂
C. C₂H
D. C₂H₂
: The empirical formula represents the simplest whole-number ratio of atoms. A
1:2 ratio corresponds to CH₂.
9. Which law forms the basis for balancing chemical equations?
A. Boyle's Law
B. Charles's Law
C. Law of Conservation of Mass
D. Law of Multiple Proportions
: Chemical equations are balanced so that the number of atoms of each element
is conserved, consistent with the Law of Conservation of Mass.
, 10. Which coefficient correctly balances the oxygen molecule in the equation
below?
__H₂ + O₂ → __H₂O
A. 1
B. 2
C. 3
D. 4
: The balanced equation is 2H₂ + O₂ → 2H₂O. Therefore, the coefficient of O₂ is
1.
11. What is the coefficient of H₂ in the balanced equation below?
__H₂ + O₂ → __H₂O
A. 1
B. 2
C. 3
D. 4
: Two molecules of hydrogen react with one molecule of oxygen to produce two
molecules of water, balancing both hydrogen and oxygen atoms.
12. Which statement best describes a reactant?
A. A substance produced during a chemical reaction
B. A substance consumed during a chemical reaction
C. A catalyst used in a reaction
D. An experimental variable
: Reactants are the starting materials that undergo chemical change to form
products during a reaction.
