Chemistry MCQs for NEET — Practice Questions with Answers

The paramagnetic species among the given options is $ O_2 ^ - $. Paramagnetism arises due to the presence of unpaired electrons. $ O_2 ^ - $ has one unpaired electron in its molecular orbital structure, making it paramagnetic. In contrast, $ CN^- $, $ NO^+ $, and CO are diamagnetic as they do not have unpaired electrons.

The VSEPR (Valence Shell Electron Pair Repulsion) theory is used to predict the geometry of molecules. This theory applies to the elements of the p-block, as it involves the arrangement of electron pairs around the central atom to minimize repulsion. Therefore, the correct answer is p-block elements.

The postulate that atoms complete their octet in the valence shell during bond formation was proposed by Gilbert N. Lewis. This is known as the Lewis octet rule, which states that atoms tend to form bonds until they are surrounded by eight valence electrons, achieving a stable noble gas configuration.

Crystal formation is typically an exothermic process. This means that energy is released when a crystal lattice is formed from ions or molecules. The release of energy occurs because the system moves to a lower energy state, which is more stable.

The lattice energy of an ionic compound depends on both the size of the ions and the charge on the ions. According to Coulomb's Law, the lattice energy is directly proportional to the product of the charges of the ions and inversely proportional to the sum of the ionic radii.

In $H_2O$ ,O Contain two lone pair of e- H Contain positive change

The strength of a sigma bond is indeed related to the overlapping of atomic orbitals. A stronger sigma bond is formed due to greater overlap between atomic orbitals. Therefore, the statement 'strength of sigma bond is not related with overlapping of atomic orbitals' is irrelevant.

Formic acid (HCOOH) and acetic acid (CH_3COOH) both have the ability to form strong hydrogen bonds due to the presence of highly electronegative oxygen atoms bonded to hydrogen. This results in a very strong hydrogen bond between these molecules.