Prelim chem help (1 Viewer)

[beeang]

Please someone help with this question:


Answer is A btw but how?

 

[fan96]

I'll have a go at the question:

1 mol CH₄ + 2 mol O₂ -> 1 mol CO₂ (the water isn't relevant here so I'll leave it out for simplicity)

Because of Avogadro's Law (equal volumes = equal moles at same temp/pressure) we can treat volumes like moles here.

So let's replace 1 mol with 50 mL.

50 mL CH₄ + 2 x 50 mL O₂ -> 50 mL CO₂

100 mL O₂ reacts with 50 mL CH₄ to produce 50 mL CO₂.

So when the gases are mixed, 50 mL CH₄ is left over and does not react.

Therefore, after the reaction ends we have:

50 mL CH₄ + 50 mL CO₂ = 100 mL gas.