MCQ 41
Which of the following represents the octet rule?
A) Atoms lose or gain electrons to achieve a full outer shell of 8 electrons.
B) Atoms can have more than 8 electrons in their outer shell.
C) Only noble gases have full outer shells.
D) Electrons must always be paired in orbitals.
Answer: A) Atoms lose or gain electrons to achieve a full outer shell of 8 electrons.
Explanation: The octet rule states that atoms tend to gain, lose, or share electrons to achieve a full outer shell of eight electrons, promoting stability.
MCQ 42
Which type of reaction involves the breaking and forming of bonds to rearrange atoms?
A) Synthesis reaction
B) Decomposition reaction
C) Combustion reaction
D) Chemical reaction
Answer: D) Chemical reaction.
Explanation: A chemical reaction involves the breaking and forming of bonds, resulting in the rearrangement of atoms to form new substances.
MCQ 43
Which of the following elements is a noble gas?
A) Oxygen
B) Neon
C) Chlorine
D) Carbon
Answer: B) Neon.
Explanation: Noble gases, such as neon, are characterized by their complete outer electron shells and are generally nonreactive.
MCQ 44
What is the electron configuration of the alkali metal potassium (atomic number 19)?
A) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
B) 1s² 2s² 2p⁶ 3s² 3p⁶ 4p¹
C) 1s² 2s² 2p⁶ 3s² 3p⁵
D) 1s² 2s² 2p⁶ 3s² 3p³
Answer: A) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹.
Explanation: Potassium has 19 electrons, with the outermost electron in the 4s orbital, characteristic of alkali metals.
MCQ 45
What is the primary type of intermolecular force in water (H₂O)?
A) Ionic bonding
B) Hydrogen bonding
C) Van der Waals forces
D) Metallic bonding
Answer: B) Hydrogen bonding.
Explanation: Water molecules exhibit hydrogen bonding due to the polarity of the molecule, leading to strong intermolecular attractions.
MCQ 46
Which of the following molecules has a linear shape?
A) H₂O
B) CO₂
C) CH₄
D) NH₃
Answer: B) CO₂.
Explanation: Carbon dioxide (CO₂) has a linear shape due to the arrangement of its double bonds, with a central carbon atom bonded to two oxygen atoms.
MCQ 47
What is the bond angle in a tetrahedral molecule?
A) 90°
B) 120°
C) 109.5°
D) 180°
Answer: C) 109.5°.
Explanation: In a tetrahedral arrangement, the bond angles are approximately 109.5°, resulting from the repulsion between four electron pairs.
MCQ 48
Which of the following best describes an exothermic reaction?
A) Heat is absorbed from the surroundings.
B) Heat is released to the surroundings.
C) There is no change in heat.
D) It occurs only in gases.
Answer: B) Heat is released to the surroundings.
Explanation: An exothermic reaction releases heat, resulting in an increase in temperature of the surroundings.
MCQ 49
Which type of bond involves the sharing of electron pairs between atoms?
A) Ionic bond
B) Covalent bond
C) Metallic bond
D) Hydrogen bond
Answer: B) Covalent bond.
Explanation: A covalent bond is formed when two atoms share one or more pairs of electrons, typically between nonmetals.
MCQ 50
Which molecule is an example of a polar covalent bond?
A) O₂
B) Cl₂
C) H₂O
D) N₂
Answer: C) H₂O.
Explanation: Water (H₂O) has a polar covalent bond due to the difference in electronegativity between hydrogen and oxygen, leading to a dipole moment.
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