a. If 2.9 x 1024 molecules of hydrogen gas reacts with excess nitrogen gas, what volume of NH3 should be produced

Question

Balanced chemical equation: 2 NH 3 (g] → N2(g]+3 H2(g)

b. If 88.5 L of ammonia gas is trapped and measured, what is the percent yield of ammonia in this equation

Answer 1

2NH₃(g) ==> N₂(g) + 3H₂(g) ... balanced equation

(a) As correctly pointed out by Anthony T.,the temperature and pressure are not given for this problem so we will assume standard temperature and pressure. Of course, at different temperatures and pressures, the volume will be different. Tell whoever gave you this question that it cannot be answered as it is presently written.

Assuming standard temperature and pressure (STP), we have the following:

2.9x10²⁴ molecules H₂(g) x 1 mol H₂ / 6.02x10²³ molecules = 4.82 moles H₂ gas

4.82 mol H₂ x 2 mol NH₃ / 3 mol H₂ = 3.21 moles NH₃ formed

At STP 1 mol of ideal gas = 22.4 L, therefore..

3.21 moles NH₃ x 22.4 L/mol = 71.9 L

If 88.5 L is trapped, this is clearly greater than 71.9 L so it would be greater than 100% yield. This is not possible.