PA S S A G E -I V : The molecular mass of a substance is the relative mass of its molecule as compared with the mass of a carbon-12 atom taken as 12 units. The molecular mass of a substance indicates the number of times one molecule of a substance is heavier than `1/12` of C-12 atom. It is equal to the sum of atomic masses of all the atoms present in a molecule. Depending on the number of atoms of same or different elements present in the molecule, it can be monoatomic, diatomic, triatomic, tetratomic or a polyatomic molecule.
Which is an example of a polyatomic molecule?

Options

A. `S_(8)`
B. `HNO_(3)`
C. `C_(2)H_(5)OH`
D. All of these

Explanation

To determine an example of a polyatomic molecule, we need to understand the definition and characteristics of polyatomic molecules. Here’s a step-by-step solution:

### Step 1: Understand the Definition of Polyatomic Molecules
A polyatomic molecule is defined as a molecule that consists of more than two atoms. These atoms can be of the same element (like O2, which is diatomic but not polyatomic) or different elements (like H2O, which is triatomic).

### Step 2: Identify the Characteristics of Polyatomic Molecules
Polyatomic molecules can be made up of:
- Same atoms (e.g., O3 - ozone)
- Different atoms (e.g., H2O - water, CO2 - carbon dioxide, NH3 - ammonia)

### Step 3: Examples of Polyatomic Molecules
Some common examples of polyatomic molecules include:
- H2O (water) - consists of 2 hydrogen atoms and 1 oxygen atom.
- CO2 (carbon dioxide) - consists of 1 carbon atom and 2 oxygen atoms.
- NH3 (ammonia) - consists of 1 nitrogen atom and 3 hydrogen atoms.
- HNO3 (nitric acid) - consists of 1 hydrogen atom, 1 nitrogen atom, and 3 oxygen atoms.

### Step 4: Conclusion
From the examples provided, we can conclude that HNO3 is indeed a polyatomic molecule because it consists of different atoms (1 hydrogen, 1 nitrogen, and 3 oxygen atoms).

### Final Answer
An example of a polyatomic molecule is HNO3 (nitric acid).

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