Chemistry - Study Mode

[#211] Which of the following is not a donor atom?
Correct Answer

(D) Aluminium

Explanation

Solution: 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).

[#212] What happens when a chemical bond is formed ?
Correct Answer

(B) Energy in always released

Explanation

Solution: Energy is always absorbed when a chemical bond is formed.

[#213] Mark the compound which possess ionic, covalent and coordinate bonds.
Correct Answer

(A) NH 4 Cl

Explanation

Solution: Ammonium chloride (NH 4 ) is generally considered as an ionic compound but this compound has three different types of bond. There is ionic bond between NH 4 + ion and Cl - ion. There are N-H covalent bonds. The formation of NH 4 + from NH 3 is sometimes described as the formation of a coordinate bond between NH 3 and H + , however once the bond is formed there is no difference between the four N-H bonds, NH 4 + has a tetrahedral structure.

[#214] In ice, the number of hydrogen bonds per water molecule is
Correct Answer

(C) 4

Explanation

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

[#215] Of the following compounds of calcium, the one having highest covalent character is
Correct Answer

(D) Cal 3

Explanation

Solution: Of the following compounds of calcium, the one having highest covalent character is CaI 3 .