Practice MCQ Questions and answers on Chemistry-GK

Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction. Antiseptics are generally distinguished from antibiotics by the latter’s ability to be transported through the lymphatic system to destroy bacteria within the body, and from disinfectants, which destroy microorganisms found on non-living objects. Some antiseptics are true germicides, capable of destroying microbes (bacteriocidal), while others are bacteriostatic and only prevent or inhibit their growth. Antibacterials are antiseptics that have the proven ability to act against bacteria. Microbicides which destroy virus particles are called viricides or antivirals. Sodium chloride,Used as a general cleanser. It is also used as an antiseptic mouthwash.

The most basic kind of soap is made from caustic soda and animal fat. The two are heated together, and then cooled. The process is called “saponification”. In technical terms, saponification involves base (usually caustic soda NaOH) hydrolysis of triglycerides, which are esters of fatty acids, to form the sodium salt of a carboxylate.

The Pauli Exclusion Principle states that, in an atom or molecule, no two electrons can have the same four electronic quantum numbers. As an orbital can contain a maximum of only two electrons, the two electrons must have opposing spins.

Aluminium is an acceptor atom, an impurity atom in a semiconductor, which can accept or take up one or more electrons from the crystal and become negatively charged.In semiconductor physics. It is a dopant atom that when added to a semiconductor can form a p-type region. For example, when silicon (Si), having four valence electrons, needs to be doped as a p-type semiconductor, elements from group III like boron (B) or aluminium (Al), having three valence electrons, can be used. The latter elements are also called trivalent impurities. Other trivalent dopants include indium (In) and gallium (Ga).

Energy is always absorbed when a chemical bond is formed.

Ammonium chloride (NH₄) is generally considered as an ionic compound but this compound has three different types of bond. There is ionic bond between NH₄⁺ ion and Cl^- ion. There are N-H covalent bonds. The formation of NH₄⁺ from NH₃ is sometimes described as the formation of a coordinate bond between NH₃ and H⁺ , however once the bond is formed there is no difference between the four N-H bonds, NH₄⁺ has a tetrahedral structure.

In ice, water can make a maximum of 4 hydrogen bond with the neighbouring water molecule.

Of the following compounds of calcium, the one having highest covalent character is CaI₃.

O⁺₂ has the highest bond order, shortest bond length and maximum bond strength.

There are two hydrogen bonds between adenine and thymine (A=T) and three hydrogen bonds between cytosine and guanine (G=C).