Answer
See the answer below.
Work Step by Step
Number of moles of octane:
$0.048\ g\div 114.23\ g/mol=4.20×10^{-4}\ mol$
From stoichiometry:
$4.20×10^{-4}\ mol×18/2=0.00378\ mol$ of water produced
$4.20×10^{-4}\ mol×25/2=0.00525\ mol$ of oxygen required
From ideal gas law:
$P.V=n.R.T$
Water vapor
$P=0.00378\ mol×0.082057\ L.atm/mol.K×(30+273)\ K/4.75\ L$
$P=0.0198\ atm$
Oxygen
$P=0.00525\ mol×0.082057\ L.atm/mol.K×(22+273)\ K/4.75\ L$
$P=0.0268\ atm$
