Most Repeated MDCAT Chemistry: Chemical Bonding MCQs

Explanation

This is the correct answer. When the electronegativity difference between two atoms is less than 1.7, the bond formed between them is generally considered covalent. In a covalent bond, the atoms share electrons to achieve a stable electron configuration.

Explanation

H2S has a bent geometry according to VSEPR. It has 2 lone pairs and 2 bond pairs and a bond angle of 92o degrees. The dipole moment is non-zero because sulfur is more electronegative than hydrogen and makes the molecule slightly polar. Thus, the geometry of H2S and its dipole moment are Angular and non-zero.

Explanation

The dipole moment of BF3 is zero because the molecule is symmetrical. The three B-F bonds are arranged in a trigonal planar configuration, and the electronegativity of boron and fluorine are similar. This means that the partial charges on the boron and fluorine atoms are equal in magnitude and opposite in direction, so they cancel each other out.

Explanation

According to Molecular Orbital Theory (MOT), two atomic orbitals overlap resulting in the formation of molecular orbitals. Number of atomic orbitals overlapping together is equal to the molecular orbital formed. The two atomic orbital thus formed by LCAO (linear combination of atomic orbital) in the same phase or in the different phase are known as Bonding Molecular Orbital (BMO) and Antibonding Molecular Orbitals (ABMO) respectively.

Explanation

A raindrop falling through the atmosphere forms a roughly spherical structure due to the surface tension of water. This surface tension is the “skin” of a body of water that makes the molecules stick together. The cause is the weak hydrogen bonds that occur between water molecules.

Explanation

Paramagnetism is due to the presence of unpaired electrons in the material, so most atoms with incompletely filled atomic orbitals are paramagnetic, although exceptions such as copper exist. Due to their spin, unpaired electrons have a magnetic dipole moment and act like tiny magnets.

Explanation

In AB4-type molecules, the central atom (A) is bonded to four identical atoms (B) with no lone pairs of electrons on the central atom. In this case, the geometry of the molecule is tetrahedral, which means the four B atoms are arranged around the central A atom in a regular tetrahedral shape.

Explanation

In CO2, two oxygen atoms are bonded with carbon atom and the geometry will be linear.O=C=OBut, in SO2, although 2 oxygen atoms are bonded with sulphur but due to presence of lone pair on sulphur, the geometry will be angular ( 2 bond pairs and 1 lone pair.)In CO2, both oxygen atoms exert equal and opposite force on carbon atoms, hence cancel out each other's effect. So, CO2 is non - polar.While, in SO2, cancellation does not occur, so SO2 is polar in nature.Hence, option C is correct.

Explanation

This ion has a 3+ charge, meaning it has lost three electrons. This results in a strong attraction between the nucleus and the remaining electrons, making it the smallest ion among the options.

Explanation

A carbocation is a positively charged carbon atom that is attached to three other atoms or groups. It has an electron deficiency, leading to a positive charge. Therefore, option a is correct.

Explanation

Ice floats on water because it has a lower density than water. As water freezes, the hydrogen bonds cause the structure to arrange in a form in which there are many intermolecular spaces, with H2O molecules being away from each other. A is incorrect because the bond length of H2O remains whatsoever the physical form H2O is in. The cubic structure of ice has nothing to do with ice floating on water. It can be proven from the fact that even if ice is formed in a different shape it will still float on water so, option B is also incorrect. Option C is incorrect because intermolecular forces are the same in water and ice, which are hydrogen bonds.