Animated Solution for Chemistry - s and p-Block Elements: Match List-I with List-II. $\begin{array}{ll}\text{List-I}& \text{List-II}\\ \text{(A) }{\text{Ca(OCl)}}_2& \text{(i) Antacid}\\ \text{(B) }{\text{CaSO}}_4\cdot \frac{1}{2}{\text{H}}_2\text{O}& \text{(ii) Cement}\\ \text{(C) }\text{CaO}& \text{(iii) Bleach}\\ \text{(D) }{\text{CaCO}}_3& \text{(iv) Plaster of Paris}\end{array}$ Choose the most appropriate answer from the options given below.

In the vast and fascinating world of inorganic chemistry, the s-block elements hold a special place, particularly the alkaline earth metals like calcium. Calcium compounds are not just abstract formulas in a textbook; they are the very building blocks of our modern civilization and play crucial roles in our daily lives.

This matrix match question is a beautiful test of your practical chemistry knowledge. It asks us to pair four fundamental calcium compounds with their real-world applications. Let's embark on a journey to decode each of these compounds, understanding not just what they do, but why they do it.

First on our list is ${\text{Ca(OCl)}}_2$. While its chemical name is calcium hypochlorite, you likely know it by its much more common household name: bleaching powder.

But how does it actually bleach things? The secret lies in its reactivity. When bleaching powder is exposed to the carbon dioxide in the air or treated with dilute acids, it undergoes a chemical reaction that releases chlorine gas. This chlorine acts as a powerful oxidizing agent. It attacks the double bonds in colored organic molecules (chromophores), breaking them apart and rendering the substance colorless.

Therefore, the correct match for ${\text{Ca(OCl)}}_2$ is undoubtedly (iii) Bleach.

Next, we encounter a fascinating compound: ${\text{CaSO}}_4\cdot \frac{1}{2}{\text{H}}_2\text{O}$. This is calcium sulphate hemihydrate.

Notice that peculiar $\frac{1}{2}{\text{H}}_2\text{O}$? That half water molecule is the absolute classic signature of Plaster of Paris. It is manufactured by carefully heating gypsum (${\text{CaSO}}_4\cdot 2{\text{H}}_2\text{O}$) to exactly $393\text{ K}$. If you heat it too much, it loses all its water and becomes 'dead burnt plaster', which is useless for molding.

When you add water back to Plaster of Paris, it rapidly hydrates back into interlocking crystals of gypsum, setting into a hard, solid mass. This unique property makes it the perfect material for making casts for fractured bones, statues, and architectural moldings.

Thus, ${\text{CaSO}}_4\cdot \frac{1}{2}{\text{H}}_2\text{O}$ pairs perfectly with (iv) Plaster of Paris.

Moving forward, we look at $\text{CaO}$, commonly known as quicklime or simply lime.

Quicklime is produced on a massive industrial scale by the thermal decomposition (calcination) of limestone (${\text{CaCO}}_3$) in huge kilns. Why do we produce so much of it? Because it is a primary, indispensable ingredient in the manufacturing of cement.

In a cement kiln, quicklime reacts with silica and alumina at extremely high temperatures to form complex calcium silicates and aluminates. These compounds are the active binders in Portland cement, giving concrete its incredible strength.

Consequently, $\text{CaO}$ links directly to (ii) Cement.

Finally, we have ${\text{CaCO}}_3$, or calcium carbonate. This is the very same chemical that makes up chalk, marble, and seashells.

In the context of medicine, calcium carbonate serves a very specific purpose. It is a mild, practically insoluble base. When you suffer from acidity, your stomach has produced an excess of hydrochloric acid ($\text{HCl}$). If you were to swallow a strong base like sodium hydroxide, it would severely burn your digestive tract.

Instead, we use a mild base like calcium carbonate. It gently reacts with the excess stomach acid to form calcium chloride, water, and carbon dioxide gas (which often results in a burp!). Because it is gentle and safe, it is widely used as an antacid.

Therefore, ${\text{CaCO}}_3$ matches with (i) Antacid.

By systematically analyzing the chemical nature and practical applications of each compound, we have successfully decoded the entire matrix:

A. ${\text{Ca(OCl)}}_2$ $\to$ (iii) Bleach B. ${\text{CaSO}}_4\cdot \frac{1}{2}{\text{H}}_2\text{O}$ $\to$ (iv) Plaster of Paris C. $\text{CaO}$ $\to$ (ii) Cement D. ${\text{CaCO}}_3$ $\to$ (i) Antacid

Looking at our given options, this sequence perfectly aligns with option (c). Questions like these are highly scoring in competitive exams. They don't require complex calculations, just a solid, intuitive grasp of everyday chemistry!