Question

Which of the following statements are true for pure substances?

• A. (i) and (ii)
• B. (i) and (iii)
• C. (iii) and (iv)
• D. (ii) and (iii)

Answer 1

The correct option is B

(i) and (iii)

The explanation for the correct options:

Option (B):

Pure substance: The substance which is made up of only one kind of atoms or one kind of molecule.

Characteristics of pure substances:

• Pure substances is homogeneous throughout their mass.
• It cannot be separated into other kinds of matter by any physical means.
• A pure substance cannot be separated into other kinds of matter by any physical process but a mixture can as they are impure substances because they contain more than one particle. For example, Salt solutions.
• A pure substance has a fixed composition as well as fixed melting and boiling points.
• Examples of pure substances- Gold $\left(Au\right),$ Copper $\left(Cu\right),$Oxygen $\left(O_2\right),$ Chlorine $\left(C{l}_2\right),$ Diamond, Water $\left(H_{2}O\right),$Salt, or Crystals.

The explanation for the incorrect options:

Options (A), (C), (D):

• Pure substances cannot be exemplified by all elements other than Nickel $\left(Ni\right)$ because pure Nickel is an element containing only one kind of particle.
• A mixture is not pure substance because it contains more than one kind of particles.

Hence, option (B) -(i) and (iii) is correct.