Question

Consider the following statements
(1) Limestone, chalk and marble are different forms of calcium carbonate.
(2) When ${pH}$ of rain water is less than $5.6$ , it is called acid rain.
(3) Human body works within the ${pH}$ range of $7.0$ to $7.8$ .
Which of the statements given above are correct?
(A) $1$ and $2$
(B) $1$ and $3$
(C) $2$ and $3$
(D) $1$ , $2$ and $3$

Answer 1

Hint : Calcium carbonate is a salt which can be used to prepare different things like limestone, chalk and marble. ${pH}$ is defined as the negative logarithm of the $\left[ {{H^ + }} \right]$ ion concentration. Water is a neutral which has the value of ${pH}$ of $7$ . But, the rain water has different values of ${pH}$ .

Complete Step By Step Answer:
The compound formed is calcium and carbonate is known as calcium carbonate with the molecular formula of $CaC{O_3}$ .
$CaC{O_3}$ can exist in different forms like limestone, chalk and marble. The given statement is true.
When ${pH}$ of rain water is less than $5.6$ , it is called acid rain as the value of acidic compounds has the ${pH}$ below $7$ .
Human body consists of blood and other fluids with a definite ${pH}$ value. Any changes in the ${pH}$ value leads to complications. Human body works within the ${pH}$ range of $7.0$ to $7.8$ .
Thus, all the given statements are true.
Option D is the correct one.

Note :
Calcium is a chemical element and mostly exists as a cation due to its metallic nature. It forms a molecule with the anion known as carbonate. Rain water ${pH}$ is different from normal water due to the presence of oxides like sulphur dioxides and nitrogen dioxide in the atmosphere.