CHEM 121 FINAL EXAM QUESTIONS AND
CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALE 2027 Q&A| INSTANT
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1. Which subatomic particle has a negative charge?
A. Proton
B. Neutron
C. Electron
D. Nucleus
Answer: C. Electron
Rationale: Electrons carry a negative electrical charge and occupy
regions surrounding the atomic nucleus. Protons are positively charged,
while neutrons have no net charge.
2. What is the atomic number of an element?
A. Number of neutrons
B. Number of protons
,C. Number of protons plus neutrons
D. Number of electrons plus neutrons
Answer: B. Number of protons
Rationale: The atomic number uniquely identifies an element and equals
the number of protons in its nucleus. In a neutral atom, the number of
electrons is also equal to the atomic number.
3. Which element has the electron configuration 1s² 2s² 2p⁶ 3s¹?
A. Magnesium
B. Sodium
C. Potassium
D. Aluminum
Answer: B. Sodium
Rationale: The configuration contains 11 electrons, corresponding to
sodium (Na), whose atomic number is 11. Its outermost electron
occupies the 3s orbital.
4. Which type of bond involves the sharing of electrons between
atoms?
A. Ionic
B. Metallic
,C. Covalent
D. Hydrogen
Answer: C. Covalent
Rationale: Covalent bonds form when atoms share one or more pairs of
electrons. Ionic bonding instead involves electron transfer and
electrostatic attraction between ions.
5. Which element is the most electronegative?
A. Oxygen
B. Nitrogen
C. Fluorine
D. Chlorine
Answer: C. Fluorine
Rationale: Fluorine has the highest electronegativity on the periodic
table. It strongly attracts electrons toward itself in chemical bonds.
6. What is the molar mass of H₂O?
A. 16.00 g/mol
B. 17.00 g/mol
C. 18.02 g/mol
D. 20.02 g/mol
, Answer: C. 18.02 g/mol
Rationale: Water contains two hydrogen atoms and one oxygen atom.
Its molar mass is approximately (2 × 1.008) + 16.00 = 18.02 g/mol.
7. How many significant figures are in 0.00450?
A. 2
B. 3
C. 4
D. 5
Answer: B. 3
Rationale: Leading zeros are not significant. The digits 4, 5, and the
trailing zero are significant, giving three significant figures.
8. Which equation correctly represents the formation of sodium
chloride from its elements?
A. Na + Cl → NaCl
B. 2Na + Cl₂ → 2NaCl
C. Na₂ + Cl → NaCl₂
D. Na + Cl₂ → NaCl₂
Answer: B. 2Na + Cl₂ → 2NaCl
CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALE 2027 Q&A| INSTANT
DOWNLOAD PDF.
1. Which subatomic particle has a negative charge?
A. Proton
B. Neutron
C. Electron
D. Nucleus
Answer: C. Electron
Rationale: Electrons carry a negative electrical charge and occupy
regions surrounding the atomic nucleus. Protons are positively charged,
while neutrons have no net charge.
2. What is the atomic number of an element?
A. Number of neutrons
B. Number of protons
,C. Number of protons plus neutrons
D. Number of electrons plus neutrons
Answer: B. Number of protons
Rationale: The atomic number uniquely identifies an element and equals
the number of protons in its nucleus. In a neutral atom, the number of
electrons is also equal to the atomic number.
3. Which element has the electron configuration 1s² 2s² 2p⁶ 3s¹?
A. Magnesium
B. Sodium
C. Potassium
D. Aluminum
Answer: B. Sodium
Rationale: The configuration contains 11 electrons, corresponding to
sodium (Na), whose atomic number is 11. Its outermost electron
occupies the 3s orbital.
4. Which type of bond involves the sharing of electrons between
atoms?
A. Ionic
B. Metallic
,C. Covalent
D. Hydrogen
Answer: C. Covalent
Rationale: Covalent bonds form when atoms share one or more pairs of
electrons. Ionic bonding instead involves electron transfer and
electrostatic attraction between ions.
5. Which element is the most electronegative?
A. Oxygen
B. Nitrogen
C. Fluorine
D. Chlorine
Answer: C. Fluorine
Rationale: Fluorine has the highest electronegativity on the periodic
table. It strongly attracts electrons toward itself in chemical bonds.
6. What is the molar mass of H₂O?
A. 16.00 g/mol
B. 17.00 g/mol
C. 18.02 g/mol
D. 20.02 g/mol
, Answer: C. 18.02 g/mol
Rationale: Water contains two hydrogen atoms and one oxygen atom.
Its molar mass is approximately (2 × 1.008) + 16.00 = 18.02 g/mol.
7. How many significant figures are in 0.00450?
A. 2
B. 3
C. 4
D. 5
Answer: B. 3
Rationale: Leading zeros are not significant. The digits 4, 5, and the
trailing zero are significant, giving three significant figures.
8. Which equation correctly represents the formation of sodium
chloride from its elements?
A. Na + Cl → NaCl
B. 2Na + Cl₂ → 2NaCl
C. Na₂ + Cl → NaCl₂
D. Na + Cl₂ → NaCl₂
Answer: B. 2Na + Cl₂ → 2NaCl
