Balancing the combustion equation for ethyne

Steps:

• Count carbon atoms: 2C₂H₂ provides 4 C, so coefficient for CO₂ is 4.
• Count hydrogen atoms: 2C₂H₂ provides 4 H, so coefficient for H₂O is 2.
• Count oxygen atoms on product side: 4 CO₂ requires 8 O, 2 H₂O requires 2 O, total 10 O atoms.
• Determine O₂ coefficient: 10 O atoms need 5 O₂ molecules (each provides 2 O).

Why D is correct:

• Conservation of mass in balancing equations requires exactly 10 oxygen atoms from O₂ to match products.

Why the others are wrong:

• A. 2: Supplies only 4 O atoms, violating oxygen balance.
• B. 3: Supplies 6 O atoms, leaving 4 O atoms unaccounted for.
• C. 4: Supplies 8 O atoms, short by 2 O atoms needed.

Final answer: D