[Aarondhp28]

I'm thinking that my professor has handed me a conceptual question to trip me up, but my math says that maybe I don't understand it as clearly as I should.

According to Boyle's law, since the volume of the flask does not change, the pressure does not change.
According to Charle's law, if the temperature remains constant, the pressure does not change.
But according to Avogadros law, and this is where I think my math proved what my conceptual understanding couldn't, if the mols (amount of gas) doesn't change, even if a chemical reaction occurs, the pressure doesn't change. The question on my assignment sheet is posted below.

A reaction is performed by combining 2.0L of gas A at 1.0 atm and 1.0 L of gas B at 1.0 atm in a 3L flask. The flask is sealed and over time they react completely to give gas C according to the following chemical equation.

2A(g) + B(g) --> C(g)

Assuming the temperature stays constant, what will be the total pressure after the reactions goes to completion?

Using PV = nRT, I can solve for T if I assume an amount of  moles. I could also solve for n if I assume T. Am I overthinking this? Is it simply, "according to the 3 general gas laws the pressure will remain constant since the volume, temperature, and amount of gas remain constant"?

[Corribus]

Lot of extra information you don't need.
 
If you can express the amount of moles of gas A in terms of R and T, you can then express the amount of moles of gas C. You know the final volume. Done. (I think you will probably find R and T cancel out.)

That's the way I would go about it anyway.

[Borek]

According to Boyle's law, since the volume of the flask does not change, the pressure does not change.
According to Charle's law, if the temperature remains constant, the pressure does not change.

Assuming amount of gas is constant, these are true.

But according to Avogadros law, and this is where I think my math proved what my conceptual understanding couldn't, if the mols (amount of gas) doesn't change, even if a chemical reaction occurs, the pressure doesn't change.

Assuming no change in V, T.