Question

The number of components in a binary solution are/is:
A.1
B.2
C.3
D.4

Answer 1

The number of components present in a solution is the number of pure substances (elements) in the solution. The elements may be in solid, liquid or gaseous phase or even in a mixture of these phases.

Complete step by step answer:
A component is defined as a pure substance present in a system in one or more phases. A binary solution is a solution containing two different elements. Most binary phase elements are compounds which contain equal amounts of both the elements present in it. For example, zinc sulphide contains zinc and sulphur. Sodium chloride contains sodium and chlorine. So, a binary solution consists of two elements present in it. Thus, the number of components present in a binary solution is 2.

$\therefore$ The correct option is option B, i.e. 2.

Additional information: The number of components present in a solution and the number of phases is a fundamental part of the Phase Rule. It is used to calculate the degree of freedom of a given system by using the formula: ${\text{F = C - P + 2}}$ , where ${\text{F}}$ is the degree of freedom, ${\text{C}}$ is the number of components and ${\text{P}}$ is the number of phases in a solution. In case of a binary solution, the number of components is 2. So the degree of freedom is ${\text{F = 4 - P}}$ . This means the degree of freedom can be 3 for a one-phase system, 2 for a two-phase system and 1 for a three-phase system.

Note:
Though in most cases, the number of components equals the number of elements present in the system, sometimes it is also equal to the number of ions formed by its dissociation. For example, the number of components in ${\text{N}}{{\text{H}}_{\text{4}}}{\text{Cl}}$ is 2, though 3 types of elements are present. This is because in a solution ${\text{N}}{{\text{H}}_{\text{4}}}{\text{Cl}}$ forms ${\text{N}}{{\text{H}}_{\text{3}}}$ and ${\text{HCl}}$.