Step-by-step explanation
Given
NH4NO3(s) ⇨ N2O(g) + 2H2O(g)
Volume of N2O = 0.500 L
At STP: Temperature = 273 K
Pressure = 1 atm
Solution
Step 1: Find the moles of N2O
PV = nRT where P is the pressure, V is the volume, n is the moles, R is the gas constant (0.0821 L.atm/mol.K) and T is the tempoerature
n = PV/RT
n = (1 atm x 0.500 L)/(0.0821 L.atm/mol.k x 273 K)
n = 0.0223 mol
Step 2: Find the moles of NH4NO3
The molar ratio of NH4NO3 and N2O is 1: 1
Thereofore the moles of NH4NO3 = 0.0223 mol
Step 3: Find the mass of NH4NO3
n = m/M where n is the moles, m is the mass and M is the molar mass
m = n x M
m = 0.0223 mol x 80,043 g/mol
m = 1.78 g
Answer
Mass of NH4NO3 = 1.78 g