The molecular formula of potassium nitrate is KNO3.

Explanation:
Potassium nitrate is a chemical compound that consists of three elements: potassium (K), nitrogen (N), and oxygen (O). In order to determine the molecular formula of potassium nitrate, we need to identify the number of atoms of each element present in the compound.

Potassium (K) is an alkali metal and forms cations with a charge of +1. Nitrogen (N) is a non-metal and typically forms anions with a charge of -3. Oxygen (O) is also a non-metal and typically forms anions with a charge of -2.

To balance the charges of the ions in the compound, we need one potassium ion (K+) to balance the charge of one nitrate ion (NO3-). The nitrate ion consists of one nitrogen atom and three oxygen atoms, so the formula for nitrate ion is NO3-. The potassium ion and the nitrate ion combine in a 1:1 ratio to form potassium nitrate.

Therefore, the molecular formula for potassium nitrate is KNO3, indicating that there is one potassium atom, one nitrogen atom, and three oxygen atoms in each molecule of potassium nitrate.

In summary, the correct answer is option 'B' because the molecular formula of potassium nitrate is KNO3, which accurately represents the composition of the compound.

The formula can be found by