Question

Which of the following statements are true for pure substances?
(i)Pure substances contain only one kind of particle.
(ii)Pure substances may be compounds or mixtures.
(iii)Pure substances have the same composition throughout
(iv)Pure substances can be exemplified by all elements other than nickel.

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

Answer 1

Pure substances are substances that are made up of only one kind of particle and have a fixed or constant structure and an element is a pure substance as it cannot be broken down or transformed into a new substance even by using some physical or chemical means. Examples of pure substances are steel, gold, diamond, iron, water, copper and many more.

Complete step by step answer:
Characteristics of pure substances are:
a)A pure substance is made up of only one type of particles which can either be atoms or molecules or elements or compounds.
b)The composition of pure substance is the same throughout i.e. it is homogeneous throughout.
c)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. Ex: salt solutions.
d)These substances have fixed melting and boiling points.
e)Pure substances are further divided into elements or compounds.
f)Pure substances cannot be exemplified by all elements other than nickel because pure nickel is an element containing only one kind of particle.
g)A pure substance usually participates in a chemical reaction to form predictable products.
Therefore, only (i) and (iii) are correct statements.

Therefore, the correct answer is option (B).

Note: Pure substances are further divided into elements or compounds and not compounds or mixtures. Elements are substances that cannot be broken down into simpler substances and they are mostly metals, nonmetals and metalloids whereas the compounds are formed when two or more elements combine together chemically in a fixed ratio.