Question

Why is fused calcium chloride or concentrated Sulphuric acid used in desiccator?

Answer 1

To reach the answer, we first need to understand what is the role of a desiccator and where it is used. Also, the properties of calcium chloride and concentrated sulphuric acid should be known in order to understand their role in the desiccator and why only they are used and not any other chemical compound.

Complete answer:
Firstly, we need to understand the role of a desiccator and where it is usually employed in. Speaking in layman language, it is a container that is used to store certain chemical compounds for some amount of time without letting the moisture get absorbed into the chemical compound. Hence, we can say that the role of a desiccator is to let a sample of chemical compound cool down without letting it absorb moisture.
Hence, from the very purpose of the desiccator, it can be seen that we may need certain chemicals in the desiccator that would help it to absorb moisture without letting the sample absorb the moisture. Hence, we need the chemicals which are hygroscopic in nature, i.e. they absorb moisture from the atmosphere.
Clearly, we know that calcium chloride and concentrated sulphuric acid, these both compounds are hygroscopic in nature and thus used in the desiccator.

Note:
The common usage of desiccator is seen in gravimetric titrations where after centrifugation, the compound is stored in a desiccator for storage and drying till the weight of the compound is taken. Also, the answering of the question can be done only when we know what is the property that these two compounds, i.e. calcium chloride and concentrated sulphuric acid have, which would make them usable in a desiccator.