What's the atm of gas remaining?

Question

Solid ammonium chloride, NH₄Cl, is formed by the reaction of gaseous ammonia, NH₃, and hydrogen chloride, HCl.

NH₃(g) + HCl(g) ⟶ NH₄Cl(s)

A 6.88 g sample of NH₃ gas and a 6.88 g sample of HCl gas are mixed in a 0.50 L flask at 25 ∘C.

What is the pressure in atmospheres of the gas remaining in the flask? Ignore the volume of solid NH₄Cl produced by the reaction.

*Note: I have found that the limiting reactant is HCl and the mass of NH₄Cl is 10.09 grams.

Answer 1

NH3(g) + HCl(g) ==> NH4Cl(s)

initial moles NH3 = 6.88 g x 1 mol / 17 g = 0.4047 mols

initial moles HCl = 6.88 g x 1 mol / 37.5 g = 0.1835 mold

Limiting reactant = HCl (as you stated)

Therefore all the HCl gas will be used up. How much NH3 gas will remain?

0.1835 mol HCl x 1 mol NH3 / mol HCl = 0.1835 mol NH3 used

moles NH3 gas left over = 0.4047 mols - 0.1835 mols = 0.2212 mols NH3 gas left

Now we use PV = nRT to find the final pressure

P = nRT/V = (0.2212 mols)(0.0821 Latm/Kmol)(298K) / 0.50 L

P = 10.8 atm