Question

How much does 12 liters of ammonia weighs at room temperature and pressure (293K and 100 kPa)?

Answer 1

8.38g

Step-by-step explanation:

Given parameters:

Volume of the gas = 12L or 12dm³

Temperature = 293k

Pressure = 100kPa

Unknown: mass of the ammonia gas = ?

_____ Now let us take the unit of pressure to atm:

Pressure = 100 kPa

1kPa = 0.00986923atm

100kPa = 100 x 0.00986923 = 0.987atm

Solution:

From the ideal gas law, we can find the number of moles of the ammonia gas. Using the number of moles, it would be possible to find the mass of the ammonia.

PV = nRT

n =
`(PV)/(RT)`

Where R is the gas constant and its value is 0.082atmdm³mol⁻¹K⁻¹

n =
`(0.987atm <strong> x  </strong>12dm³)/(0.082atmdm³mol⁻¹K⁻¹ x 293K)`

n = 0.493mol

We know that, mass = number of moles x molar mass

Molar mass of NH₃ = 14 + (3x1) = 17gmol⁻¹

mass of NH₃ = 0.493 x 17 = 8.38g