What is the mass in kilograms of 25L of hydrophosphoric acid?

0.0345kg is the mass of 25L of the sample

Explanation:

Hydrophosphoric acid, H₃P = Phosphine has a density of 1.38g/L.

To solve this question we need to convert the volume of the gas to mass in grams as first and then to kilograms as follows:

Mass in grams:

25L * (1.38g / L) = 34.5g

Mass in kilograms:

34.5g * (1kg / 1000g) = 0.0345kg is the mass of 25L of the sample

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.