Answer : The number of moles of oxygen gas required are, 4.49 moles.
Explanation :
The balanced chemical reaction is:

First we have to calculate the moles of butane gas.
As we know that, 1 mole of substance occupies 22.4 L volume of gas.
As, 22.4 L volume of butane gas present in 1 mole of butane gas
So, 15.5 L volume of butane gas present in
mole of butane gas
Now we have to calculate the moles of oxygen gas.
From the balanced chemical reaction we conclude that,
As, 2 moles of butane gas react with 13 moles of oxygen gas
So, 0.692 moles of butane gas react with
moles of oxygen gas
Therefore, the number of moles of oxygen gas required are, 4.49 moles.