Chemistry MCQs for NEET — Practice Questions with Answers

The reactivity of carbonyl compounds in nucleophilic addition reactions decreases with the increase in steric hindrance and electron-donating alkyl groups. Hence, the order of reactivity is: Butanone (IV) < Propanone (III) < Propanal (II) < Ethanal (I).

When ketones react with magnesium amalgam (Mg-Hg) over water, pinacols are formed. This reaction is known as the pinacol coupling reaction. The ketone is reduced to a diol (pinacol) through an intermediate radical mechanism.

In the presence of a dilute base, benzaldehyde (C6H5CHO) and acetaldehyde (CH3CHO) undergo a crossed aldol condensation to form cinnamaldehyde (C6H5-CH=CH-CHO). The reaction involves the formation of a β-hydroxy aldehyde intermediate, which then dehydrates to give the α,β-unsaturated aldehyde product.

The weakest acid among the given options is isobutyric acid ((CH3)2CH COOH). The presence of electron-donating alkyl groups (CH3) reduces the acidity of the carboxylic acid group by increasing electron density around it and thus making it less likely to donate a proton.

The most acidic compound among the given options is o-hydroxybenzoic acid. This is because of the intramolecular hydrogen bonding which stabilizes the conjugate base, making it easier for the compound to lose a proton (H+). In o-hydroxybenzoic acid, the hydroxyl group at the ortho position relative to the carboxyl group helps to stabilize the negative charge on the oxygen atom after deprotonation, increasing its acidity.

In a carbon atom, the electronic configuration is $1s^2 2s^2 2p^2$. The 2p orbital has two unpaired electrons. Therefore, the number of unpaired electrons in a carbon atom is 2.

inert pair effect is most prominent in Pb because from top to bottom due to increase in number of shells.

SiCl₄ (Silicon tetrachloride) has a tetrahedral structure. For a molecule or ion to be isostructural with SiCl₄, it must also have a tetrahedral geometry. PO₄^3- (Phosphate ion), NH₄⁺ (Ammonium ion), and SO₄^2- (Sulfate ion) all have tetrahedral structures. However, SCl₄ (Sulfur tetrachloride) has a seesaw shape due to the presence of one lone pair on sulfur, and thus it is not isostructural with SiCl₄.

In crystalline lattice of diamond, each crbon atom is linked to four other carbon atoms tetrahedrally by using sp3 - hydbrid orbitals giving rise to a rigid there dimensional network of carbon atom for this reason, diamond is very hard.Graphite, has hexagonal layer structure in which each carbon atom is linked to three other carbon atoms by using sp2 hybrid orbitals. The hexagonal layer in graphite are held together by weak Van-der waal's forces. So graphite is soft.

$ CCl_4 + H_2O \rightarrow$ No reaction d - orbital absent in carbon atom