Molar mass of N2 = 28
Moles of N2 = 25 / 28 = 0.89
So, moles of NH3 produce = 2 x 0.89 = 1.78
Note: H2 is in excess. so no need to care about it.
Charged particles or ionic particles?
Example:
Mass = ?
Density = 25 g/mL
Volume = 5 mL
therefore:
d = m / V
25 = m / 5
m = 25 x 5
m = 125 g
hope this helps!