Question

Which of the following is not a mixture but a compound?
a.) Soda water
b.) Sea water
c.) Soil
d.) None of above

Answer 1

Hint: Let us recall what we learnt about matter in our previous classes. Anything around us which has some mass and occupies some space is known as matter. It is made up of very small particles called atoms and molecules.


Complete step by step solution:
Now, matter can be classified into two fundamental types:
Pure substances : Pure substances are made up of only one kind of particle and have a fixed or constant structure. Pure substances are further classified into two types, Elements and Compounds.
Impure substances or Mixtures: Impure substances or mixtures are made up of different kinds of elements combined together or more pure substances mixed together in any proportion. Impure substances or mixtures are further classified into two types, homogeneous or heterogeneous.

If we take a look at our option:
Soda water: It is a mixture of water (liquid) and dissolved carbon dioxide (gas). It also contains added sweetener (solid component). All these elements are not chemically bonded.
Sea water: Sea water is a mixture of compounds as it contains sand and dust (silicates), mineral salts (sulphates, chlorides, nitrates). Sometimes it also contains pollutants.
Sea water: It is also a mixture as the basic components of soil are minerals of sand, silt or clay. It also contains organic components such as bacteria and fungi.

So, the correct answer is (d).

Note: We should not get confused between compounds and mixtures as compounds are pure substances which contain atoms of different elements chemically combined together in a fixed ratio while mixtures are impure substances, made up of two or more physically mixed substances.