Question

Observe the diagram, state and explain under which category this chemical reaction falls.

Answer 1

Limestone is most commonly known as calcium carbonate. It is kind of carbonate sedimentary rock, mainly composed of minerals like calcite and aragonite.

Complete answer:
- Limestone is an extensively versatile mineral. It is a carbonated sedimentary rock formed on the seafloor where materials rich in calcium carbonate get accumulated.
- Limestone is also known as calcium carbonate since it is the main component.
- It is even a part of the diet of terrestrial animals and is added in the diet of poultry animals to improve egg quality.
- When limestone undergoes metamorphism, it crystallizes to form marble.
- The given diagram shows strong heating of limestone power.
- As limestone is heated, the calcium carbonate present inside it absorbs heat. This indicates the reaction proceeds as an endothermic reaction.
- After heating, limestone granules breakdown and decompose to form calcium oxide (quick lime).
- Reaction involved is shown below

$$\begin{aligned} CaCO_{3}(s)\xrightarrow{\Delta }CaO(s)+CO_{2}(g) \end{aligned}$$

- This reaction is a type of thermal decomposition and the process is known as calcining.

Additional information:
Marine organisms like coral leave their calcium carbonate shells behind as they die. This is the reason why 10% of the sedimentary rocks are limestones.

Note: Limestone is soluble in water and weak acids. When mixed with water, it gives slaked lime. It even contains variable amounts of silica in the form of chert.