Compound ${\text{KN}}{{\text{O}}_{\text{3}}}$ is also called:
A. Nitre
B. Bengal saltpetre
C. Chile saltpetre
D. Both A and B

Hint:To answer this question we should kno the meaning of the Nitre and saltpetre words. Both, Nitre and saltpetre words represent the salt of nitrates. Potassium nitrate is found in Bengal mainly and sodium nitrate is found in chili mainly.

Complete answer:
The chemical name of ${\text{KN}}{{\text{O}}_{\text{3}}}$is potassium nitrate. It is an ionic salt. Potassium is an alkali metal. so, it is also an alkali metal salt. Potassium nitrate is a salt of nitric acid because when potassium hydroxide reacts with nitric acid gives potassium nitrate and water.

The naturally occurring salts of nitrate which are present in form of powder and found in rocks and soil and used in fertilizers, gunpowder are known as saltpetre or saltpetre. As the nitrates are the source of nitrogen so, saltpetre are also known as nitre. The Latin word of saltpetre is “sal petrae” which means salt of the rock.

The potassium nitrate is a salt of nitrate, so it is known as saltpetre of nitre. Potassium nitrate is mainly found in Bengal and Bihar, so it is known as Bengal saltpetre.So, ${\text{KN}}{{\text{O}}_{\text{3}}}$ is also called Nitre and Bengal saltpetre.

Therefore, the correct answer is (D).

Note:Saltpeter, saltpetre, Niter, Nitre all are the same. All these words are used for salt of nitrate but the Bengal saltpetre and chili saltpetre are different salt of nitrate. Potassium nitrate is very famous as a gunpowder because it is used in the formation of gunpowder. Potassium nitrate is also known as nitrate of potash. The sodium nitrate is known as chili saltpetre because it is mainly found in Chile and Peru region.