Chemistry MCQs
Topic Notes: Chemistry
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
1
Determine the total number of pi (π) and sigma (σ) bonds present in a benzene molecule.
Answer:
3π and 12σ
Benzene (C6H6) consists of a hexagonal ring of six carbon atoms. Each carbon is bonded to one hydrogen atom via a sigma bond (6 total) and to two adjacent carbons via sigma bonds (6 total), totaling 12 sigma bonds. The alternating double bonds contribute three pi bonds, as each double bond consists of one sigma and one pi bond. Thus, the structure contains 12 sigma bonds and 3 pi bonds.
2
Only sigma bonds are present in__________________?
Answer:
ethoxy ethane
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3
Which compound exhibits hydrogen bonding?
Answer:
C2H5OH
Hydrogen bonding occurs when a hydrogen atom is bonded to a highly polarized atom, like nitrogen, oxygen, or fluorine. Among the given options, ethanol (C2H5OH) has a hydrogen atom bonded to an oxygen atom, enabling it to form hydrogen bonds. Ethane (C2H6) and chloroethane (C2H5Cl) do not exhibit hydrogen bonding, and methane (CH3OCH3) only has a single hydrogen bond, not the two required for significant hydrogen bonding properties.
4
What type of isomerism does propene exhibit?
Answer:
none of the above
Propene is an alkene with the general formula C3H6. It does not exhibit cis-trans isomerism because it is a symmetric molecule. Geometric isomerism is also not possible in propene as it does not have a double bond with restricted rotation. Hence, propene does not exhibit any type of isomerism mentioned in the options.
5
Pi bonds are produced by overlapping of__________________?
Answer:
Un-hybrid orbitals
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6
Which of the following processes involves the addition of hydrogen molecule across carbon-carbon multiple-bond?
Answer:
hydrogenation
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7
Which of the following is not an unsaturated hydrocarbon?
Answer:
C5H12
C5H12 is a saturated hydrocarbon, whereas the other options are unsaturated hydrocarbons. Unsaturated hydrocarbons have one or more double bonds between carbon atoms, whereas saturated hydrocarbons have only single bonds.
8
The bond length of C=C is___________?
Answer:
1.68A°
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9
What is the hybridization of the nitrogen atom in pyridine?
Answer:
Sp2
Pyridine is a planar, aromatic molecule, and the nitrogen atom is part of the aromatic ring. Its hybridization is Sp2, which allows for the formation of three bonds and is consistent with the molecule's planarity and aromaticity.
10
Crystalline solids can be identified easily from their ___________________?
Answer:
Sharp melting point
A valid JSON object explaining the original MCQ and its options follows: Crystalline solids, also known as crystals, are substances that have a repeating three-dimensional pattern of atoms, ions, or molecules. One characteristic that helps differentiate them from other solids is their distinct sharp melting point. This sharpness indicates a specific, well-defined bond breaking and formation process, unlike the gradual change seen in amorphous solids. Among the provided options, the correct answer is 'Sharp melting point'. This is because the sharpness of the melting point is a unique feature that helps identify crystalline solids.