Combustion oxygen requirement from balanced equation

Steps:

• Use combustion formula for CxHyOz: CxHyOz + (x + y/4 - z/2) O2 → x CO2 + (y/2) H2O, with x=3 for all.
• Calculate O2 for each: propane C3H8 (z=0) needs 3 + 8/4 = 5 O2.
• Propanoic acid C3H6O2 (z=2) needs 3 + 6/4 - 1 = 3.5 O2; propanone C3H6O (z=1) needs 3 + 6/4 - 0.5 = 4 O2.
• Propan-1-ol C3H8O (z=1) needs 3 + 8/4 - 0.5 = 4.5 O2, matching the given requirement.

Why D is correct:

• Propan-1-ol's formula C3H8O yields exactly 4.5 O2 molecules in the balanced combustion equation.

Why the others are wrong:

• A. Propane requires 5 O2 molecules, exceeding 4.5.
• B. Propanoic acid requires 3.5 O2 molecules, less than 4.5.
• C. Propanone requires 4 O2 molecules, not matching 4.5.

Final answer: D