QJEEAdv78Ch235d: JEE Advanced 1978 Chemistry - Class 11 JEEAdv78Ch235d Solution: A compound was found to contain nitrogen and oxygen in the…

To determine the formula of the compound, we first need to understand the concept of empirical formula. The empirical formula represents the simplest whole-number ratio of atoms of each element in a compound. Given that the compound contains nitrogen (N) and oxygen (O) in a ratio of 28 g of nitrogen to 80 g of oxygen, we can use the following steps to find the empirical formula:

Step 1: Convert the masses of nitrogen and oxygen to moles using their atomic masses. The atomic mass of nitrogen (N) is approximately 14 g/mol, and the atomic mass of oxygen (O) is approximately 16 g/mol.

$$\text{Moles of N}=\frac{28\text{g}}{14\text{g/mol}}=2\text{moles}$$

$$\text{Moles of O}=\frac{80\text{g}}{16\text{g/mol}}=5\text{moles}$$

Step 2: Determine the simplest whole-number ratio of the moles of nitrogen to the moles of oxygen by dividing both by the smallest number of moles:

$$\text{Ratio of N : O}=2:5$$

This ratio suggests that for every 2 moles of nitrogen, there are 5 moles of oxygen. Thus, the empirical formula of the compound can be represented as $N_2O_5$ .

Therefore, the correct option is Option C: $N_2O_5$ .