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.