Here's how to calculate the moles of molecules in 250g of hydrogen nitrate (HNO₃):

1. Find the molar mass of HNO₃

* Hydrogen (H): 1.01 g/mol

* Nitrogen (N): 14.01 g/mol

* Oxygen (O): 16.00 g/mol (x3 since there are 3 oxygen atoms)

Molar mass of HNO₃ = 1.01 + 14.01 + (16.00 x 3) = 63.02 g/mol

2. Calculate the number of moles

* Moles = mass / molar mass

* Moles = 250 g / 63.02 g/mol

* Moles ≈ 3.97 mol

Therefore, there are approximately 3.97 moles of hydrogen nitrate molecules in 250g.