Solution:

For 15 g of nitrogen gas (N₂), where the molar mass \( M = 28 \, \text{g/mol} \):

1. Calculate the number of moles, \( n = \frac{\text{mass}}{\text{molar mass}} = \frac{15}{28} \).

2. Using the ideal gas law \( PV = nRT \):

\[
PV = \frac{15}{28} RT
\]

So, the equation of state is \( PV = \frac{15}{28} RT \).