Question

An unknown substance ‘A’ on thermal decomposition produces ‘B’ and ’C’ . What is ‘A’ – an element, a compound or a mixture ? Give reason to support your answer.

Answer 1

Hint: To answer this question, we first need to understand what substance is. A chemical substance is a type of stuff with a predictable chemical makeup and behaviour. Physical separation procedures, i.e., breaking chemical bonds, cannot separate a chemical substance into its constituent elements, according to some references.

Complete answer:
Element - An element is a pure substance made up entirely of atoms with the same number of protons in their atomic nuclei, as defined by chemistry. Chemical elements, unlike chemical compounds, cannot be broken down chemically into simpler molecules.
Compound – A chemical compound is a substance made up of numerous identical molecules bound together by chemical bonds and made up of atoms from different elements. As a result, a molecule made up of only one element's atoms is not a compound.
Mixture - A mixture is a composition made up of two or more distinct components that have not been chemically mixed in chemistry. A mixture is a physical mixing of two or more substances that retain their identities and are blended in the form of solutions, suspensions, or colloids.
Because A decomposes, it cannot be an element because elements do not decompose.
The word 'thermal decomposition' would not be used if it were a mixture because it describes a chemical change. As a result, A must be a compound.
So the final answer is that ‘A’ is a compound.

Note:
Thermolysis, or thermal decomposition, is a chemical degradation caused by heat. The temperature at which a substance chemically decomposes is known as its decomposition temperature. Heat is necessary to break chemical bonds in the substance being decomposed, hence the reaction is frequently endothermic.