Help! chemistry volume problems.?

Question

question #1)
If 50 liters of nitrogen (N2) weighs 56g and 50 liters of hydrogen (H2) weighs 4.0g, how much would 50 liters of ammonia (NH3) weigh?


question #2)
Let's say 22.4 liters of helium (He) weighs 4.0g. At the same temperature and pressure, 22.4 liters of oxygen (O2) weighs 32.0g. How much would 22.4 liters of hydrogen (H2) weigh? Hint: look carefully at a periodic table.

Answer 1

First question:

1.- The reaction here is:

N2 + 3H2 -------> 2NH3

1 mol of N2 plus 3 moles of H2 yield 2 moles of NH3

2.- Let's see how many moles we have in the given weights:

n(N2) = 56 g / 28 g/mol = 2 moles
n(H2) = 4 g / 2 g/mol = 2 moles (limiting reactant)

3.-The number of moles of Ammonia obtained from 2 moles of H2 are: 1.5 moles, and we know that 1 mol of any gas in Normal conditions are equal to 22.4 L, so 1.5 moles are equal to 33.6 Liters.

Hence:

mass(NH3) = n(NH3)* M(NH3) = (1.5 moles)(17 g/mol) = 25.5 grams.

then, 33.6 L - 25.5 grams
...........50 L - x

x = 37.94 grams

4.- Conclusion: 50 liters of NH3 under the same given conditions weigh 37.94 grams

Second question:

22.4 L (equal to 1 mol of H2) weigh 2 grams

Good luck!