Chemistry - Complete s-block Question with Solution | TestHub

The correct answer is Special ppt. $\mathrm{CaC}{\mathrm{O}}_3$. Precipitated calcium carbonate (PCC), often referred to as "special ppt. $\mathrm{CaC}{\mathrm{O}}_3$," is widely used as a filler and coating pigment in high-quality paper manufacturing due to its brightness, opacity, and printability-enhancing properties.

Explanation:

Calcium carbonate ($\mathrm{CaC}{\mathrm{O}}_3$) is a common filler in paper. Natural ground calcium carbonate (GCC) is derived from mining. However, precipitated calcium carbonate (PCC) is synthetically produced and offers superior control over particle size, shape, and surface chemistry. This allows PCC to impart higher brightness, opacity, and smoothness to paper, making it ideal for high-quality grades. Calcium hydroxide ($\mathrm{Ca}(\mathrm{OH}{)}_2$) is slaked lime, used in some industrial processes but not directly as a paper filler. Calcium bicarbonate ($\mathrm{Ca}(\mathrm{HC}{\mathrm{O}}_3{)}_2$) exists only in solution and is not a solid material used in paper manufacturing.